First off, you are not an idiot.

And your relationship with her can be quite distinct from her relationship with that other friend or even from your relationship with that other friend. It is up to you whether you still want to 'fix' things with her.

You are also not to blame for keeping your distance when she reached out to you. You were doing the best at the time for your mental sanity (for want of a better word). I see that as good self-care. Frankly, she has not been consistent and has been rather disappointing as a supposed 'friend' to you. So, I don't think you should beat yourself up for not responding immediately when she decided to contact you.

She has to meet you half-way. This is what good friends do. Even if one messes up, it is all about give and take and sticking with the other. If she resents you for not contacting her immediately, I think that says a lot more about her than about you...