Here are some options.
First pick up the "Latitude 40" maps of Moab east and west. You can pick them up in town (look for Eddie McStiffs brew pub on the main street, there is a map store accross the street to the north) or you can get them
HERE
My suggestions for rides:
Gemini Bridges Not technical, nice sights, some slickrock (nothing hard) and a big parking area right off the highway. This area is about 4 miles north of town right off the highway and there is a big marker at the trail head.
Klondike Bluffs This is 9 miles north of Town on the main higway leading into town. Take the road north and stop on the south end of the bridge. There is a parking area. Go through the Gate and ride in. The first couple of miles is road (you could even take the RV in if not muddy) the trail is not technical and winds it's way to the border of Arches national park (no bikes allowed) There will be a dead end, park the bikes and walk in (about 1/2 mile) totally amazing views and totally worth it.
Slick Rock/Fins & Things / Porcupine Rim This is a bit more technical, Slickrock is not bad but lots of steep up and down. You can do the practice loop 1.4 miles before deciding weather she wants more. If you like that you can ride straigt to Fins & Things or over to Porcupine Rim although PR is much more rocks and ledges.
MAKE SURE YOU LEAVE TIME TO SEE ARCHES NATIONAL PARK!!!
Rod