She won't stop touching her vagina

My daughter is fully potty trained. But to get us there we did no diapers and no underwear. She wears dresses so she can run to the potty and just easily sit, wipe, go.

So now...she won't wear underwear at all and is CONSTANTLY touching her vagina and sometimes her butthole. Like she's touching all of it, and making it red. I understand the "she's just figuring out her body" but this habit needs to stop. It is all day. When I say anything to her she screams.

I need help with tips to get her to stop. And to get her to start wearing underwear.

I asked a friend if her daughter did this and she said no then insinuated that my daughter has been abused. That is not even possible. She has never been out of my care in her almost 3 years of life. Not even for an hour.