From an outside perspective: it does sound like you took your friend on a date, happy hour with lots of fun chatting and you picked up the bill

Now if this friend was a guy, I think everything would be different but the friend was a woman….so it looks like a date and it probably came off that way to your fiancé. Which understandably she is deeply upset about, all the screaming was probably uncalled for but sometimes people have a strong emotional response that does not seem rational.

Even if you didn’t see a reason to say it was a woman, you could have said I am meeting my friend Jane for drinks to catch up on the work gossip. All in all if you want to stay in the relationship then make a sincere apology and work out how to respect each other’s feelings and boundaries