is being friends with your husband's ex-gf realistic?

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my husband has an ex-girlfriend that i knew personally. well, i just knew leslie (the girl's name) because she added me to her friendster account. then, we chatted occasionally thru Y.M., then exchanging cellphone numbers, and eventually, meeting in person. being friends with her wasn't bad at all. for me, that is. though admittedly, i was a bit jealous and insecure with her because she and my husband has been with for almost two years, but a lot had happened between them on that period. although a lot of people would wry whenever i tell them i was friends with her and although my husband declared a big NO NO on this friendship, it still went on secretly. yes, i do care and pity to her life stories (she has no father and plunges to one relationship to another after her and my husband's breakup), but still, im a little concerned about her real intentions on being friends with me. i like to be her friend. but sometimes, im being cautious.. the question: would it really be possible to be friends with your present's past?