All you need really is to find the correct bike fit dimensions. Id go and get her to try similar bikes in your local bike shop. Note the names and check their geometry online or tape measure in store.
Or simpler. Measure the TT and stem on her current bike. Then compare online geometry. They all publish the geo of their bikes.
Eg here https://www.boardmanbikes.com/products/529-y1415-sls-9.0-fi.html
By the sounds of it all you need to get right is the top tube length/reach. You change TT/teach by fitting shorter – longer stem. In her case Id guess shorter stem.
As I said you change the length with the stem.