52 cm, if long legged will be a really good fit. If torso long then it is a bit more difficult.
I will also say build it up as a road bike with brifters on hand. And I would possibly use some slightly Randonneur bars you can find, and the shortest stem you have on hand (60/70). Try the 30s on the wheels. If they fit, those are plenty wide.
She can learn spots on the bar that are most comfortable.
And you can always call @
gugie to have him modify it for cyclocross!