When will I stop feeling angry? (Post break-up)

In September, my girlfriend and I broke up. To make a long story short, she was avoidant. In the weeks leading to the break up, she began treating me quite coldly. I made attempts to remedy the lack of connection, but ultimately it was clear she was no longer interested in the relationship. I went to her house to talk it out. She wouldn't tell me out right what was going on. I basically had to keep offering up possibilities, if that makes sense. "Is it work?" "Is there something that I've done?" Things like that. I asked if she still wanted to be with me and she said I don't know. I asked if she needed some space she said "what does that mean?" I said I don't know, that's why I'm coming to you. I really couldn't get a clear answer. In the end, she said she didn't want me "gone forever". The lack of clarity and certainty was clear enough, though.

I'm leaving a lot out, but this was a Saturday. Cried all weekend. I called her Monday and she said she wanted to be "friends for now". At the time, I said it was fine. I was distraught for a bit, ugly crying and all, but I worked through it. It fucked me up, though. We talked about marriage and made plans for our future. Then, on a random Tuesday, she just tapped out. I no longer feel hurt nor do I want her back, but I am still so angry. Thinking about her just irritates me. I was in the store earlier and saw a drink she likes and though "ugh". I'm kind of over feeling this way. When does it end?

This is my first real break up, so I'm a bit naive. From everything I've read, anger is just part of it, but for how long?