This is a hard one to answer, and depends what sort of site she has. We stayed at 3 campgrounds in Yellowstone in the summer of 2017 (Grant, Canyon, and Fishing Bridge) in our 28 ft motohrome (29'5" bumper to bumper), and booked 30 ft back in sites at all 3 campgrounds, they ranged from barely long enough down to I am amazed we fit. One was so short that I put out orange marker cones by the front bumper as we were so close to the camping loop road I was worried we might get clipped by someones towing mirrors. Also as of 2017 the 30 ft sites we had at Canyon and Grant Campgrounds were just that, about 10 ft wide and 30 ft long, with no place to park a detached second vehicle, with saplings growing up at the edge of the pavement all around, so no overhanging the back of the site, and probably no place to put out slides (we don't have any). Only the site we had at Fishing Bridge had a shorter space next to it for a second vehicle. Out of the 3 so called 30 ft sites the longest one we had was maybe 32 ft overall.
This was very different from the pull though site we had at Mather Campground at the Grand Canyon in 2019, which was advertised as 27 ft max, though was in reality about 75 ft long, though arching and somewhat narrow, and a tight turn at the entrance, and was probably really limited to about 30-31 ft without clipping a tree or rock entering the site, which just goes to show these site measurements can be off both ways.