Welcome to the wonderful world of women! :p
Lady K is on point...probably a very immature/unhealthy person...or someone going through a really hard time. I think it has less to do with personality type and more to do with maturity and coping skills. I actually had a great INFJ boyfriend and it really drove him away because I had difficulty dealing with something, and like others said, he was the only person available at the time to vent to.
Not to stereotype INFJs or anything, but they have a tendency to want to heal and protect people (especially INFJ guys). They expend a lot of emotional energy wanting to help people realize their potential that it runs them ragged. It was that way with my BF. He wanted to be there for me, but there was nothing he could really do to help me because the issues at hand were out of our control. But he felt obligated to fix everything and he took it so hard upon himself that he just could not bear to see me upset at all (it reminded me of him when you mentioned her behavior is "Detrimental to your psyche"). What she needs is, as Lady K and Teddy stated, is someone to just listen to her and validate how she feels, even if you do not agree with it. Listen, but be detached and don't feel like you have to fix all her problems. I agree 100% with what Teddy said about how to deal with it.
A lot of women, not just ISFJs, LOVE to vent and HATE it when men try to fix things. When I am in vent mode, I am basically doing it because I am backed into a corner, all my options suck, and there is nothing I can do about it. If I could have fixed the problem, it would be fixed and I would not be venting; therefore, any advice people try to give just comes across as trite, unless I specifically ASK for advice.