If she does heavy squats and other glute exercises, and increases her caloric intake, she'll gian muscle in her thighs and ass. The problem with most girls who try to squat and workout, they don't consume an excess of calories or protein in order to build the muslce, so it doesn't change that much for them. They think they'll get huge like Arnold or somebody if they lift heavy and eat a lot of protein and shyt. So it's possible for her to grow more ass, but not likely because most females in the gym won't grasp this and work at it.
Also, just look at track bytches, the sprinters. They all have ass and thighs, it's not by coincidence, it's from the activity they're doing.