hey biggy
see the first thing i would think about is that its great her friend told u that she liked u but u should know more. does she show that she has interest in you like body, signs, flirting, touching, closeness? if you notie any than she should be in interest of you. but of course you dont want to all of a sudden ask her out one day.slowly build up and to the point where your close with her ask her out where you feel confident. but make sure you know what ur doing. being in another relationship mean your commited and to spend time with her and listen to what she has to say. if you cant do those things you could end up breaking her hear and loosing a friend. so i hope you do whats right 8)