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.