My sister's wedding is tomorrow, and I don't want to go

My life is an absolute mess right now, and I pretty much lack any motivation or drive to do anything, (even small stuff like chores.) Without getting too personal, I lost my mom last year and it's taken its toll on me and my family. She really was the glue that held us all together, and now that she's gone, I rarely speak to or see any of my siblings.

I'm currently living with my dad, and my sister lives in a neighboring state, but there's no bad blood between us or anything. My dad suggested driving up together, but Ive never had the best relationship with him, as growing up, I was always much closer to my mother, and if I'm being honest, 6 hours in the car with him doesn't sound great.

I could drive up separately, but as selfish as it sounds, I don't want to spend the money on gas. I also just quit nicotine a couple months ago, and unlike the state I live in, the sale of flavored vape juice isn't banned where she is. I know it sounds silly, and admittedly it's a pretty stupid excuse, but I don't want to risk putting myself in a position where I could potentially make a bad decision.

I know this post is very "woe is me", but I'll admit that I'm a selfish person, and I don't want people to make the mistake of thinking they can rely on me. Even though it may not come across in this post, I do genuinely love and care about my sister, but of all the weddings I've been to in my life, only one marriage has lasted. If I decide not to go, I know she'll take it personally, and I don't even know what I'll tell her.

I'm not in a good place right now, and most days I don't even understand myself, so any advice would be appreciated.