Found out my roomate's GF used to be a mega-ho

[Nologo]

Talking to Maria about it first is the absolute worst thing you can do. If Joe finds out later, and she mentions that YOU knew and didn't tell him, it'll be a huge problem between you two.

You probably shouldn't say anything. As [censored] up as it may be, when guys are that in love with a woman, they tend to side with her over even their best friends. It'll probably lead to you being alienated, regardless of whether or not they stay together.