If she disappears once she is angry, it could even be a coping mechanism to relax herself and not destroy friendships by blowing up as someone who doesn't deserve it.

I know that I withdraw if I'm frustrated, stressed out, depressed, etc. I put in the effort to tell people that I'm not ignoring them.. that I just need time on my own.

Some people are understanding of that, and others don't care and just get upset if they don't see or hear from me for awhile. It can make things worse, but I've been working on handling that and deciding they aren't worth my time.... but it makes me feel like a failure.

If you want to be better friends with this person, you could always try asking them.