Interesting, but I have heard of it happening
I understand. My 3 year son doesn't like underwear. I made a deal with him. He can sleep with them off at home as long as it is at home. I am not sure why small kids go through this but I have met other mothers who have kids that like sleeping naked at 3-4 yrs old. I thought maybe his underwear was too tight but I bought some fun underwaer for him, different cartoon characters. You may want to make a deal with her and tell her she can do it here but not out. I dont know if it would work for you. Also we let him pick the his underwear that he wants to wear for the day. Since he sleeps alone it has been easier for us. Believe me our son would go to sleep and wake up crying. He did not want anything near his private area. It was not until we compromised with him about making choses. Since then he sleeps with his fun underwear. We also run into this issue once in a while