I feel like valgus collapse always takes a while to correct. The first thing I was going to say was Lateral X-Band Walks which are similar to Monster Walks. Also continue to do hip and ankle mobility. Try to foam roll the lower body before and after training (IT band, VMO, Quads, etc).
Also, I would try to incorporate single leg squatting movements. Split Squat and Bulgarian Split Squats with the barbell on the back.
Other than that just continue to do those different exercises with her because it's something that's just going to take some time.