Moving away, having to deal with the inevitable

My GF and I have been dating since freshman year of college. We're both seniors now. I am moving very far away for my job, and she is not going to come with me: she has to take another semester to finish school and she cannot move that far away from her family, whom she is very close with.

We decided that we are going to break up in a few months. But now that the date is approaching, things have started to get pretty tough. We are arguing a lot. She's afraid that I'm starting to care less about her and take her for granted. She has pretty bad emotional problems (bipolar, depression, anxiety,) and I'm having a lot less patience with helping her with these problems, consoling her, dealing with fights, etc.

Altogether I think these next few months are going to be more bad than good. We know that our relationship is going to end, and it seems to be causing a lot of emotional stress. Ultimately, I want to end things on the best terms possible. I want her to remember having a good relationship with me, rather than one that totally fell apart in the last few months.

For these reasons, is it a good idea to end it now? Or could this cause her to be resentful? Is this a legitimate reason to break up?