Question about big girl undies :)

Hey everybody, my little girl angel is 3 years old and doing great on potty training, with her big girl undies, but is it normal for them to get kinda " stuck " to the skin, when being pulled down ? Like the middle part is kinda stuck, whilst the sides easily slide down her legs, she does get a bit sad when it happens, since she wants to pull them off herself. Any of you perhaps also encountered this problem ? Please reply if you do. 
Love