Since she ASKED for your advice, I would tell her the same thing I tell everyone; Go to an RV show and see what you like and make a list out what amenities she has to have.
If she's buying used, I always suggest they avoid anything that smells like mildew (even if it isn't visible) or has had a leak. There are plenty of units out there that you don't have to deal with this headache with. Don't trust what a salesman or the nicest couple tell her about a rig. Verify everything and perhaps even hire a professional to check it out (if used).
