One, if they did talk a lot, then your cousin was aware her roommate did stuff like that, so why would your cousin set you up knowing her roommate was a temptress?

Or, they didn’t talk, so you wouldn’t have had to worry about the cousin finding out whether you went along or not.

Have you ever told your cousin what happened? What did the roommate do when you rebuffed her advances? Did she keep coming after you? Was she mad? Or more like, “too bad, your loss.”