I've had this best friend for over a year now and at first she was amazing. She really helped me when I was struggling due to my autism and my mental health (such as with panic attacks), and even defended me in front of a group of girls who were bullying me and had left me in tears for months. I honestly thought she was an incredible friend and sat for hours on the phone with her, mostly to keep her company but also because I enjoyed it.
Then this year happened. Our friendships been steadily deteriorating for months, beginning in February when I started to feel extremely uncomfortable and truthfully hurt after I went all the way to where she lived (over a four hour journey) for what I had believed to be a birthday celebration only to feel forgotten for the entire week. Her and our other friend chose what we watched, listened to, ate and did, and all I'd wanted to do was go for one drink at a bar we like but we didn't even do that despite spending over six hours in town for them going to the shops they wanted to go to. I felt pretty sad when I came home as I've always had issues celebrating my birthday (a lot of trauma around it) and she'd promised me it would be a big celebration and whilst I appreciated the gifts I got I felt like there had been no point me going up.
I tried to keep calling her but I was really struggling to sit on the phone all day with her as I was unable to focus on my writing whilst doing so.
Then, in April, she became pretty nasty, sending me a horrible text when I wasn't sure I could make a meet up after having a meltdown and accused me of not considering her autism for a previous trip as we left "early" when I had let everyone invovled know when I would have to leave beforehand and accused me of not understanding her struggles. I apologised profusely whilst she complained in a group chat we're both in (didn't name me thankfully) and subtweeted me on twitter. She tried to call me the next day and said I wasn't being fair by not picking up the phone so I replied and said I was hurt and needed some space. She did not like this at all, continued to try and call over the next few days and got friends to check in with me and blamed me for her poor mental health because I didn't feel comfortable talking to her. It all hit a head when we were all on holiday and I was screamed at by her and another friend. I ran to my room as I was having a panic attack and on the verge of crisis and she followed refusing to leave even when my partner asked her to. Since then, she's been very hot and cold. She's made passive aggressive digs when I haven't text her back quick enough / when I haven't called, saying I'm not there for her, checking my likes on tiktok because I wasn't sending her videos, and has become obsessed with my favourite tv show in a way that reminds me of my old friend who did something unforgivable to me last year. She's blocked both my partner and my other best friend from viewing her instagram stories, has shouted at me over small things and I constantly feel on edge and like I'm walking on eggshells around her. I'm scared to call but if I don't she gets worse. I don't know what to do as we're going to canada in september alone and I don't feel comfortable going with her but I can't be refunded the money I've already spent. I'm soon to book flights which was an issue when discussed as I don't think I can handle a changeover and she got very cruel about it and acting like I was being deliberately difficult.
Sorry this is so long I am just terrified of going on holiday with her but I can't pull out as she will be unbelievably angry with me and truthfully I'm not in the mental headspace to handle it as the root of my mental health issues stems from PTSD from an abusive friend in my childhood. I don't know whether I should be friends with her or not, whether I'm the real problem or whether she's behaving inappropriately. I feel like I'm going crazy and constantly in fight or flight mode which is causing me to be exhausted and get poorly often.
Any adivce on how to cope with this friendship as I know I can't stop being friends with her would be appreciated, as I can't talk to her about the issues we're having as when I have tried in the past she has blamed me for her behaviour and it took me repeating multiple times that she hurt me for her to say sorry.
Sorry if this is worded badly, I've tried my best but it's so difficult to explain everything.