I (30/M) was stood up by best friend (29/F)

Hello reddit, longtime lurker and throwaway here. First off, my best friend and I used to be romantic. Her and I say we are strictly platonic but if the environment allows it, we will get frisky. I love her like a best friend, and I love her kids dearly. They are extremely close to me and her family feels like family.

This year has been hell. Work, home, and financials have been out of control for me, but she is always there for me. She started seeing a new guy at the beginning of summer. She always told me about the guys she was seeing and I've met and been cool with them all. Except this guy(41/M). Many long nights of her telling me of mental abuse, harassment, lying, cheating, trying to lose his job, alcoholism. One time he said he was so upset, he called his ex to "verbally eviscerate" her over the things he was mad about my best friend did. She even threw her phone at me and said "Deal with him" when he wouldnt stop calling her while we hung out. He told her that we text too much, and suddenly we nearly stop communicating.

So here is my problem. I was in a serious accident and I'm now dealing with some loss. She said she was coming over with the kids to hang. I couldn't be more excited. It was exactly what I needed. Hours go by and there's no word. No texts or phone calls. I figure I'd give her space because she does live a busy life and things had been hectic. I check out social media and she is at a bar with that guy. If there was ever a time I needed her support and the sweet smiling faces of those munchkins, it was then. It was extremely hurtful.

She apologized and I forgave her, but that doesn't mean Ive let go of my anger. I told her its not fair for me to keep blowing up on her and that we shouldn't talk. She came over with the kids and I of course loved seeing them, but we went back to talking after that day and I still havent let go yet.

Does it get easier? I don't want to lose her or the kids.

tl/dr - bestie stood me up and I can't let go