Hi. Poor thing, bless her.
Somethings that helped…
We limited sugar, increased fluids, and were prescribed Hydromol to use for shower and baths (you can also purchase from local pharmacy for about £8-12 depending on size). We also increased more baths rather than showers. Some toilet papers can cause irritation too.
Not much help now, but one doctor said they grow out of them.
If was a little red, Sudacrem seemed to soothe over night too.
Look into vulvovaginitis.
Also, 100% cotton underwear washed on 90 (I am sure 60 would be fine). Made sure was a full load but if not, made sure they went on a rinse and spin to make sure detergent was removed.
Bought tights with highest cotton content.
I know some of the above seem over the top but you feel so helpless and desperate, that you try everything.
I hope your little one, feels better soon and that you get to the bottom of it.