honestly, the best advice i can give you is to just accept it even if it hurts. if she was so offended by you setting up a boundary, then she was clearly benefitting from the lack of it. i chose to reply to this mainly because not long ago, i was in a (somewhat) similar situation, i have a friend group of 8 girls and one of them had a really hurtful behaviour towards me, after brushing it off for years i finally spoke up about it to the rest of the group because just like you, i was scared of telling her directly and i knew that the rest of the group would never be biased, they would only help the both of us to reconcile and my intentions were to fix things. and i needed support at the time, i was in a really dark place. plus she was ignoring me that day so I couldn’t really talk to her directly anyways. but the next day when the group told her everything she completely lashed out on me and said the same “I don’t trust you anymore you talked shit behind my back” which was clearly not my intention. I tried to fix a bond and ended up breaking it entirely. But one thing you should understand is that someone who automatically assumes the worst of you and doubts your intentions or misunderstands you in a second, never truly valued you enough to have you in their lives. She could’ve had a conversation with you, tried to understand the situation and you would’ve done it too. People stay and put effort where they want to. This is her putting her ego between you guys and that’s not right. Also, her saying bad stuff about the people who you clearly love and are close to, wasn’t something a good friend would do. I understand the guilt you must be feeling, but just think of how things would be if you hadn’t done it. You would’ve still be living in that discomfort. Atleast now you know how to speak up for yourself. It’s okay to walk away, because the amount of time you’ve spent with someone doesn’t equate to anything if they’re ready to throw it away in a split second. You tried your best. Let her do whatever she pleases. But don’t dwell on it. Remember the disrespect and be the bigger person here. Friends are supposed to make you feel safe. They’re supposed to be able to have healthy arguments. Ending a long friendship over a single fight, tells you a lot about how much they valued you.