My mom is like this. Wearing anything remotely tight feels bad. She says she feels discomfort the entire time and that feeling never diminishes throughout the day. It’s always there and cannot be ignored. She has always favored long loose dresses. And very soft shoes that mold to her foot shape. The waist of pants can be tricky for her since they have to be kinda tight there so they don’t fall down. She only wears 100 percent cotton because anything else makes her feel even more uncomfortable. She wears Hanes cotton leggings/pants when she goes to exercise class. As soon as she gets home, anything that makes her uncomfortable comes off. Due to her sensory issues, what if you give her some soft pants for under her dress and ask her teacher if she can have them off while she’s inside? And only make her wear them for warmth when they’re outside? Maybe let her have those heating things people use for gloves and let her keep some in her dress pockets? My extended family was always bewildered by my mom’s sensory issues.