It's hard to say. Depends on the bike, the setup, and her proportions. You can get a rough idea of whether her torso is much shorter than yours or not by comparing inseams. If her inseam is much longer than yours, she probably needs a smaller frame. (Because her torso is relatively smaller for the same height).
As to bike frame size --
I'm 5'6".
I have a 52cm Bianchi Axis that fits me perfectly. It has a 53.9 cm virtual top tube. I'm running a 90mm stem with a substantial positive rise, maybe 10 degrees.
I also have a 49cm Scott Contessa CR1 pro that fits me beautifully. It has a 51.5 cm virtual top tube. I'm running a 120mm -6 degree stem on it.
The Scott is a much more aggressive position with much more saddle-bar drop, but both bikes fit me well and they are very different frame sizes and setups.
So it's just hard to say . But it's worth a try. It seems at least plausible that your bikes could fit her.