Haha. It has nothing to do with holds being polished, that's the nature of the schist found on Mt. Mansfield and elsewhere in the Greens. It sure ain't Adirondack anorthosite or White Mountain granite. You guys are spoiled.
Csprague, based on the description of your girlfriend' needs, I like Roy's suggestion of Camel's Hump. The Monroe Trail is an excellent choice. The Burrows Trail would be, too, but it would be a much longer drive.
If someone has severe difficulty with feeling exposed on hiking trails, and/or rough, rocky footing, then I would definitely not recommend Laura Cowles. While the Maple Ridge trail is a mighty fine trail, there might be one or two short stretches where such a person would have difficulty and almost the entire trail is rock, much of it open. The same is true for Sunset Ridge (there are one or two rock scrambles on Sunset Ridge, which I'm guessing might prove difficult). In fact, if your girlfriend is uncomfortable with rocky surfaces, I would avoid the West side of Mansfield altogether.
The Long Trail would be fine, except that there are one or two exposed feeling scrambles in the last couple hundred vertical feet. Certainly the Haselton>Toll Road>Long Trail would be no problem at all. The Haselton isn't a bad trail, but the upper section is loose gravel in the middle of a ski trail and isn't aesthetically pleasing.
P.s. Make sure to stop at the Cabot Outlet between Wateerbury and Waterbury Center on Route 100 , on the West side of the road, for all-you-can-eat free cheese and other snacks. Grazing is encouraged! The Cold Hollow Cider Mill on the East side of Route 100 is also another good stop with free food samples and cider. The cider donuts are excellent, though not free.