it depends. how long have they been friends? do they have history? do they flirt? Is she single? Are you sure you aren't jealous of her? I need a little more information to give a worthwhile opinion. At the end of the day, if it makes you unhappy and you expresses it to him, he has a decision to make. You or Her.
@Dr.JuliaChicken Men and women can be "just friends". there maybe initial temptations but once you get by them, it can be a valuable "just friends" friendship. But it doesn't mean it will be.
@lilypjmom2122 trusting your gut is always a good idea. its the safe way out as it makes you be content in your decision. but it doesn't mean it was the right decision. do a lil investigation if you must. remember this is a life changing situation. you cant just say "i am sorry" if you are wrong. Its just not that simple.
just my opinion.