With women there are a few things to consider.
Its gonna lower her estrogen levels
its mildly anabolic.
So you could stop her menstrual cycle and feel not so great
She could also develop hair in unwanted places and enlarging of the clitoris....deepening of the voice.
This is the same for pretty much anything anabolic/androgenic
It has been studied extensively in women because it was a breast cancer medication.
Safety rating is very good.
Potential sides....up to you if you want to risk em.
Shes not gonna grow a beard after a couple weeks on formeron though.