White residue with redness
and strong odor is not normal.
At any time were these tests done?- Urine microscopy or culture, swab from the vaginal area?
Urinary infection has to be ruled out.
Since you say, its going on for some time- yeast infections
in the vaginal region must also be looked into. If its a long standing yeast infection, its better to have the blood sugar done at least once.
If blood sugar is high, long standing or repeated yeast infections can happen- which are extremely itchy and on repeated scratching- skin will get denuded- resulting in burning sensation and pain.
Along with this proper hygiene should be maintained.
Give her soft cotton underwear only. It should not be tight.
And as the last thing- its better to be sure that there is no form of sexual abuse- especially if your kid is away from your sight even for some part of the day.
Hope my answer helps you.
Please feel free to get back if you have further queries.