Am I overreacting by throwing this friendship away?

So i'm an 18 year old female, currently having problems with my best friend who is also an 18 year old female.

So, very recently, my friend (X) started seeing a mutual friend (Y). They had already been pretty good friends and he had pursued her before, but she rejected him or he changed his mind or some bullshit. I can't remember.

Anyways, so they start being "together", since apparently they're not official. I know i can't stop them, but i feel like it was stupid of them to get together. One reason is that there is a significant age gap, Y is over 30, Y has gone through 4 marriages and has children in all of them. He comes with a ridiculous amount of baggage and i feel like he just wants X to "fix him," which i believe is impossible at this point without professional help.

This isn't what's bothering me, i should just get to the point. So X went back home for Christmas and i hadn't had a chance to see her in a couple of weeks. We had been pretty close, hanging out often and always sending a text here and there. So she finally came back into town the other day, i hit her up asking if she had gotten in yet. She responded 2 hours later with a one worded text saying, "Yeah." I then asked her if she still wanted to hang out, considering we had already made plans, but she never got back to me.

Alright, whatever, so she fell asleep at Y's place, understandable. He was probably the first person she wanted to see when she got into town, i get it. I'm just miffed that she didn't take the time to at least text me about it... Something you must know about me, i absolutely DESPISE when people flake out on me like that. I've had a lot of problems in past relationships (both with friends and romantic relationships) with this, there is nothing that makes me feel more insecure than when someone flakes out without even taking the time to tell me.

So i finally get a hold of her the next day. I ask if she wants to hang out and she said not till later in the day cause she was hanging out with Y. I brush it off again, trying not to overreact. To tell the truth, Y and i haven't been getting along lately. I'm in a shitty place right now, the short winter days really get to me and always make me feel awful. Along with this, i've been in a shitty rut lately, so i wasn't feeling too hot. Y always insulted me, saying really hurtful things. Along with calling me fucker and other such lovely names, he always threw really hurtful things from my past in my face. When i was 15, i was a pretty big slut. It's a shameful part of my past and i don't like thinking about it, but he loves throwing it in my face after i told him in confidence. For instance, when we were going to the movies together, i asked him if he wanted to sneak some candy in my purse or something like that. He responds with, "I'd just stick it in your vag, it's probably big enough to hold it. But it'd probably just fall out since you're so loose." Ow. What the fuck? There are plenty of more things he's said, such as, "Oh don't fuck that guy, i know since he talked to you, you feel inclined to."

So i tell X about this and explain that i don't want to be around Y. So she's like "Oh, well fuck Y, he's a dick." About 30 minutes later, she calls me up asking if i want to have lunch with her and Y. This really pissed me off, so i responded again with, "No, i told you i don't want to be around Y." She hasn't talked to me since.

I'm super fucking bummed out. I spent a lot of time on her present. We had made plans to exchange gifts on the day she first blew me off. I'm just really hurt about all of this. I always try my hardest to be the best friend i can to her. Hell, i drove in a fucking blizzard because she needed help with her school papers. And then she just throws me aside for this fucking dick?

Am i in the wrong to just cut her out of my life? I feel like i always give back so much but hardly ever get anything in return.

TL;DR: Supposed best friend blows me off for dickish boyfriend who would be verbally abusive towards me. Should i say fuck it and cut her off?

Sorry if i rambled and such... This is actually my first post on here.