It’s really going to depend on the bike and the model. For instance, Felts are on the long and low side, while something like a Cervelo is I think shorter front to back but taller proportionally. I’m about 5’3" (with thick socks on), and I ride a size 49 cm Lapierre (road bike), a 47 cm Felt DA1 (tri bike), and a 45 cm Felt ZW95 (road bike). I’m a little short in the leg and long in the torso, so those models/sizes might not work as well for her.