Simple solution. Don't make her wear underwear if she does not want to. No one is required to wear underwear and certainly should not be forced to simply because society dictates it.
A related discussion,
Underwear statement was started.
Dear Wedgie:
I just saw your post from July. Did your 4 year old ever grow out of this? How is it going? My 4 and a half year old refuses to wear underwear. For about a year she just complained about them sticking up her butt. Like you, I tried several different types but nothing satisfied her. But it was just within the last month that she started changing her underwear everytime she went to the bathroom (she claims her urine leaks, but I never feel any wetness). Now she just won't wear them at all. She doesn't seem to care if she gets discipline,- she just doesn't want to wear any underwear. I'm curious as to whether this is just a stage. Any advice?
Dear Wedgie:
I just saw your post from July. Did your 4 year old ever grow out of this? How is it going? My 4 and a half year old refuses to wear underwear. For about a year she just complained about them sticking up her butt. Like you, I tried several different types but nothing satisfied her. But it was just within the last month that she started changing her underwear everytime she went to the bathroom (she claims her urine leaks, but I never feel any wetness). Now she just won't wear them at all. She doesn't seem to care if she gets discipline,- she just doesn't want to wear any underwear. I'm curious as to whether this is just a stage. Any advice?
Given the severity of her response, you might proceed with an evaluation by an occupational therapist to investigate the possibility of sensory integration problems, particularly some version of tactile sensitivity or defensiveness.
I went through a similar thing with my son. We had a lot of testing done and we found out he has sensory intergration dysfunction. The best people to test for this is a pediatric occupational therapist. Your local childrens hospital should have an OT in the deparment who tests for this. The earlier you catch this the easier it is to help correct. Above all stop fighting with her - she may truelyy be uncomfortable.