Well, several times I typed out responses, and each time I deleted them. I don't really know how to help you, since that has never happened to me. Seems to me that girls are a LOT more prone to jealousy than guys.
What I would do is just distance myself from that person. That's usually what I do when I have any problem with a person though. I have no tips on how to remain friends with a person while not being jealous anymore
Just try and make a conscious decision that you won't be jealous of her anymore. Every time you feel jealousy just stop and tell yourself that you don't care and you aren't going to be jealous any longer.
Not much, but that's the best I could come up with...