I'm pretty sure I ruined someone's relationship last night
Did you feel guilty about ruining this relationship?
No, it was just two friends of mine.
Friends are expected to be there for one another, not ruin each others relationships. If they find out what you did, they'll stop being friends with you.
I think they will overreact and be okay with it later.
It's okay if your friends have a negative reaction to your actions. You should apologize to them instead of assuming they will get over it. You shouldn't mess with your friend's relationships.