Am I wrong for considering skipping my stepsister's wedding because I feel excluded from her life?

I’m a 24-year-old woman, and my stepsister is 28. She is getting married next year, and I’m seriously considering not attending because I’ve started to feel like I’m much more invested in our relationship than she is.
I want to make clear that I understand she has every right to choose her own bridesmaids and decide who she wants involved in her wedding. I don’t believe I’m entitled to be a bridesmaid simply because we’re stepsisters. My issue is more about what the situation has made me realize about our relationship.
I’ve known her essentially my entire life. My mom has been in her life since she was born, and I’ve heard her introduce me to people as her sister many times. She has also called me her stepsister, while she consistently refers to her biological half-sister simply as her sister.
She is now getting married and has around eight bridesmaids. I am not one of them. One of her bridesmaids is a friend who is 24, and her biological half-sister is also 24.
She hasn’t asked me to be involved with bridesmaid duties, and she recently talked about going dress shopping without me. She also talks about the gifts and dresses she is buying for her bridesmaids.
I know none of this is technically wrong. It is her wedding.
But it hurts because I’ve always thought of our relationship as being closer than this.
I’ve helped her move out of both apartments she had with her boyfriend. I was one of only three people who consistently helped her move, and I showed up even when it was physically difficult and a huge inconvenience. If she eventually moves out of her current three-story condo, I already know I’ll probably be there helping her again because that’s just how I am with people I care about.
I’ve also tried to support her wedding.
She told me she was doing a photography shoot, so I made her a Pinterest board with more than 1,000 wedding ideas and over 200 photography ideas. I added photography concepts, wedding ideas, and potential dresses because I thought it might help her stay organized.
I wasn’t expecting anything in return. I genuinely wanted to help.
She did thank me by text after I sent it, so I don’t want to exaggerate and say she completely ignored my effort. But she hasn’t really discussed the ideas with me or involved me in the wedding planning.
There is also some history between us that makes the situation more complicated.
For the most part, we get along when she’s sober. However, I’ve had some very negative experiences with her when she has been drinking or using drugs.
A couple of years ago, we were on a family trip and she drank so much that she needed to be pushed around in a wheelchair. I’m not a big person, and physically pushing or moving heavy things is something I genuinely dislike doing, but I helped her anyway without complaining.
While I was pushing her, she repeatedly yelled at me, “Push me, bitch.”
The way she said it felt aggressive rather than playful. I was uncomfortable and felt disrespected, but I continued helping her. My family was recording some of it, and the next day they showed her the video. She laughed but never apologized.
There was also an incident when I was 14.
She was over 18 and had been trusted to take me to a concert. My mom paid for our tickets. At the concert, she offered me cocaine and ecstasy that she had gotten from a stranger, despite knowing I was only 14 and had never used either drug.
I didn’t take them.
She then disappeared for most of the concert after doing drugs with a random person she had just met. I was 14, couldn’t find her, and kept trying to contact her. I remember feeling very unsafe and abandoned.
I eventually brought this incident up during a family argument years later. She was upset that I told our parents about it, and I don’t think she has ever forgiven me for bringing it up. I have mostly forgiven her and tried to move forward, but she has never apologized for what happened.
Despite all of this, I’ve continued trying to have a normal relationship with her.
The reason I’m struggling so much with the wedding is because I’m thinking about the future.
If we know each other our entire lives, eventually we’ll be in our 70s or 80s and our parents won’t be here anymore. We may have to deal with our parents’ house, our own marriages, children, family events, and all the major things that happen over a lifetime.
I keep thinking about looking back when we’re old and realizing that we weren’t actually part of each other’s important moments.
Maybe that is overly sentimental. I don’t know.
But right now, I honestly don’t want to go to the wedding.
I don’t want to skip it as revenge. I don’t want to make her wedding about me. I don’t want to tell her, “You didn’t make me a bridesmaid, so I’m not coming.”
I’m considering not going because I genuinely feel hurt and disconnected from the relationship, and part of me thinks it would be easier emotionally to step back rather than attend while pretending everything is completely fine.
At the same time, I’m worried that not attending would make me the asshole.
I also worry that my absence might not even matter to her, which honestly makes me feel worse.
I know that people aren’t obligated to include me simply because I’ve been kind to them. I know helping someone move doesn’t mean they owe me a bridesmaid position. I also know that not being a bridesmaid doesn’t automatically mean someone doesn’t care about you.
But when I put everything together—the way I felt excluded from my cousin’s wedding and bachelorette party, my stepsister having eight bridesmaids and not including me, not being invited dress shopping, and some of our past interactions—I can’t help but feel like there is a larger pattern of me caring more about these relationships than the other person does.
So, \*\*Am I wrong if I decide not to attend my stepsister’s wedding because I feel hurt and excluded from her life?\*\*
Would it be better to simply attend as a guest, be happy for her, and accept that we’re not as close as I thought?
Or would it be reasonable to step back from the relationship and decline the wedding invitation without making it into a confrontation?
I genuinely want honest opinions, including if I’m being overly sensitive or making this about myself.

\*\*Update: A similar situation actually happened with my cousin’s fiancé, who also didn’t make me a bridesmaid or invite me to the bachlorette party while almost every other female cousin around my age was included. Looking back, I regret attending. I still attended the wedding, but it honestly made me feel pretty hurt and shocked immediately upon arrival, I realized that all of the other female cousins were lined up together as flower girls at the entrance except me. It was extremely awkward walking in and seeing everyone included while I was the only one left out. Later, while the flower girls, bride, and groom went off-site to eat, I was basically left sitting there without food, which made me feel even more uncomfortable and unwanted. Not knowing where\*\* \*\*they went. I also felt awkward taking pictures if my parents were in them because I already felt like I wasn’t really wanted there. The bride and groom never asked me to get in them but asked my parents. Then, at the after-party, my uncle almost got into a physical fight with someone, which made the whole night even more uncomfortable. Because of that experience, I have a feeling my stepsister’s wedding could end up making me feel similarly. I’m already worried that I’ll show up and feel like an outsider again. Another thing I noticed with my cousin’s wedding was that I wasn’t given a separate invitation with my name on it. There was just one invitation sent to our house. I have a feeling the same thing may happen with my stepsister’s wedding invitation, which would honestly reinforce the feeling that I never received a formal invite unlike everyone else. Also, I would never attend an event just for the free food or cake. I can afford to treat myself to nice things, so I wouldn’t force myself to go somewhere or go out of my way to attend something simply because there’s free food involved. I generally just do things at my own pace, and I’m grateful that I’m blessed enough to be able to take myself out and enjoy nice things every now and then.\*\*

Also, just wanted to quickly add that I’ve never asked her to help me move to or from my apartment. I was honestly scared of creating tension, and since I enjoy working out anyway, I never really said no when she asked me to help. But going forward, I’ve decided I’m not going to assist her with moving anymore if she asks. I’ll probably just say I already have plans so I can avoid unnecessary tension. I don’t want to feel like people can just walk all over me.
Also, with the Pinterest thing, I already had that account because I was saving wedding ideas for myself, and I told her that. It wasn’t something I created specifically for her. I just thought it would be helpful and mentioned that there were a lot of ideas on there that I thought she’d like.
And lastly, I don’t have the best relationship with my family. Her biological father, who is my stepdad, abandoned her for a few years during her childhood, and he’s abusive, along with my biological mother. I’ve chosen not to go completely no-contact with them, but honestly, I don’t really care that much about what they think of me. A lot of my family are alcoholics and have very different values from me.
For example, they’re going to a Chris Brown concert soon, which is personally something I would never feel comfortable supporting because I don’t feel right supporting someone who has physically abused women. They didn’t invite me anyway—my stepsister is the one organizing it, and they invited my 16-year-old cousin.
Honestly, I really don’t want to go to the wedding. Family weddings have tended to be pretty stressful for me, and I don’t really feel like putting myself through that just to keep everyone else happy.
Because they’re disorganized, loud, untamed, and specifically with my step sisters it feels like I’d be a burden if I came and I don’t really even feel like going. If I were to not go to the wedding I’d say I had a trip planned etc and be out of town for sure or make plans with my friends, so let me know what you think would it really be a big deal? I truly don’t want to attend and I don’t think she’d care if there was a legit reason like being on vacation.