Well you know me - I'll throw in for Trek. When I first got back into riding I told the kid I hadn't ridden road bikes in years and I was going to use it for commuting blah blah blah. Bless his heart he listened to what I said - which wasn't what I meant! (my bad) He sold me a 26" comfort bike which was sweet and heavy as an ox and not at all what I wanted. I probably would've been happier with the Trek Hybrid which is heavier than a road bike but uses skinnier tires and is built more for speed than a comfort bike. It also sits up vs a road bike if she's concerned about flexability.
She might do better going to different bike shops and talking to them. I'm currently riding a vintage Trek 50 cm frame which fits my 5'2" height perfect but it isn't a WSD nor have I ever ridden one. Maybe offer to go with her if you have the time and she seems intimidated by the process.
Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, champagne in one hand, strawberries in the other, body thoroughly used up, totally worn out and screaming: "Yeah Baby! What a Ride!"