I have a flashbang bra holster for my LCR and its OK. Its just not my favorite place to carry my LCR. I could definitely get to if needed and sometimes choose that as my BUG.
I'm a big girl too and her problem isn't going to be the gun or type of holster it's going to be where she wears it on her hip. I find my Kahr and my S&W both conceal well just off my hip at about 4 o'clock. I have another big girl friend who likes hers at the appendix.
I do prefer OC over CC but find that CCing creates a nice personal game. Like a deep conceal game - can they tell I'm carrying?
There's also a bra holster by Well Armed Woman that sorta tucks the gun on the side of the bra instead of underneath the girls. She might want to look at that along with the flashbang. I forget what they call that holster.
She's just going to have to experiment with IWB, belly bands, flashbangs, fanny/belly packs and purses until she finds what works for her gun, body and comfort level.