I'm a girl and have kind of been in the same situation... in fact I still kind of liked my ex-boyfriend till a few months back... it sucks, yes, and I myself felt guilty for such betraying feelings... I love my boyfriend a lot, that I do not doubt, but feeling anything towards my ex kills me on the inside and if I don't tell my present bf about it, then it makes me feel unfaithful towards him...my ex and he were (hopefully are) friends... he doesn't show the pain or hurt which he feels when I talk about my ex and that sucks the most... I try and avoid meeting my ex and seeing him as best as I can... that seems like the only solution to me... your gf can't exactly do that but ask her if she can keep it to a minimum... maybe that'll help...
