when such happened that i am thinks upon all situation and wisely take step.i know such cases mind not works only hearte's requisite comes at first place but then after I felt uncomfortable

with them both being in my home at the same time....I would ask him not to bring her over

.If he asks why,tell him,bcz she is my friend too, and I feel like I'm betraying her with this dirty little secret you have.I also feel like you are over stepping your bounds in this friendship by basically asking and assuming that I will lie for you to cover it up.That's not friendship, that's being used.I'd want to know, and to be honest,the boyfriend would never know how I found out.....I'd just tell him that it's time for us to part ways ....only that i am can do in this matter