As a short rider myself (5'4"), I find the geometry around 26" wheels to be the most comfortable, but your partner may have different preferences and/or proportions.
I found a couple of interesting bikes on CL in your area:
https://ksu.craigslist.org/bik/d/manhattan-youth-road-bike-ready-to-ride/7398734186.html
https://kansascity.craigslist.org/bik/d/overland-park-trek-fx-72-hybrid/7392639989.html