<human>: I live with a lesbian couple. A few weeks ago, one (let's call her Britney) cheated on the other (let's call her Christina). Britney went away with a "friend" for a week, and when she returned she confessed to having spent the entire week cheating with her friend (who she knows from her work). Britney has moved out while they take a break to "figure things out".

Christina still wants to be with Britney. I don't know what to tell her. I know from living with Britney that she's a selfish and immature person who took advantage of Christina. Christina however just sees Britney in a positive light and still hopes that things will work out.

I don't know what to say, or how to comfort her. I'm sad for her, and I know i should just stay out of it, but I can't accept the idea of Britney coming back and continuing to hurt my friend.  I've never heard of someone being so brutally cheated on, and still want to have a relationship. What should I do?

Can you provide a brief rundown of the text in within 3 sentences?
<bot>: Roomie was cheated on, still wants to be with cheater, how can I be a good friend in this situation?