I just said, "I am those women's friend". Whatever else the merits and drawbacks, this translation has the virtue of avoiding the preposition altogether...
Also: I don't know what the original "main" answer was, but I'll just throw in my two cents to the effect that "I am a friend of those women" sounds fine to me.
I had this one as a Type What You Hear exercise, but if it had been a translation instead, I automatically would have gone with "I am a friend of those women" (which, as it happens, is also the literal translation). Easier, I think, than the "friends with" construction, though that phrasing would certainly be used in English, too.
When there are more then two persons involved přítel is usually really just a friend. When you refer a person of the opposite gender as "můj přítel", "moje přítelkyně", that is most often really a romantic partnership. I am not too sure about same-gender partnerships but I think they often say "můj partner", "moje partnerka" to make it clear they are more than just a friend (but partner/partnerka is used for straight partnerships as well.)
To, co se říká česky, s tím přece nemá nic společného. Jde o to, co se říká anglicky. https://www.helpforenglish.cz/article/2015091101-friends-mates-buddies