The OP thinks Ben Cleugh is too much and you guys are suggesting Beinn A’ghlo 🙁 Don’t do that unless she has excellent stamina and fitness
Glen Garr and Dunkeld are good suggestions. The Glen Fincastle route from Pitlochry is also good. All Dougals suggestions are spot on. Dumyat in the Ochils is better than Ben Cleuch tho will require some local knowledge and probably a bit of walking to get the best day out feel.
Good fun in the wee hills at the back of Perth as well – as long as you dont stray onto the downhill course
masses of stuff around aviemore/rothiemurchas which is ideal for any level – go and visit Bothy Bikes for ideas – also some nice riding around Comrie – go and visit Comrie Croft for ideas – tho their trails will probably be too difficult there are loads of tracks in the area.