its not usually ok, but it wasnt a proper relationship if it lasted 17 hours so i think its fine, that rule only really counts if it was like proper dating

I went out with my best mates ex-girlfriend once and no-one had a problem with it. We were all 11 though lol.
I doubt there would be a problem if it lasted for 17 hours and he was pissed.

I don't know.
If they broke up, don't you think it would kind just kind of awkward that when you all our hanging out together, she has to put up with her ex boyfriend.

I believe in that rule because I want the best for my friends and to put them before any other guy.

Why not... You are free to do it...

Just ask your friend if its okay.