I would feel betrayed too, it was a secret.
Maybe she just wanted to keep the chat going and had nothing juicy to say, women chatting will do that.
Men say ~7,000 words a day, women ~20,000 , it appears that there endofings release in women’s blood stream when they talk, that bring them pleasure.
I would let her know it was wrong and start to worry about the other women !
Remember once you open a can of worms you will need a can twice as big to get those little buggers back in.
All the best.
Hugs
JudyK