just to shed some light on things. when she told you about the proposal about him, how did you take it? did you get jealous and grumpy or laugh it off? maybe depending on how you reacted whenever he is brought up, that is why she said she couldn't talk because of you?

granted that it sucks that she has to hide her calls talking to him from you, but i had a roomate once who's boyfriend would go balistic whenever her ex called her. now, she had everything in check, no feelings for him but wanted to be his friend, but her bf at the time would go crazy whenever he found out the ex called.

so, that being said as with everyone else so far, do what you feel you must. and if you can trust her then do so.