I had sex with someone who’s partner has mono

i'm terrified. i did not realize how contagious it was even before symptoms show. me (f) and my friend (mtf) had unprotected sex and her girlfriend (mtf) who is on vacation was just diagnosed with mono. my friend and her girlfriend have not had sex for a month, me and my friend have shared cigs. she currently has no symptoms. what the fuck do i do? (yes it is an open relationship)