I think that the most likely cause for your daughter's vagina hurting when she wipes would be irritation, either from the pads or something else.
Assuming that your daughter hasn't had sex, there isn't anything serious that is likely to be the cause.
Many sanitary pads contain a variety of chemicals and other substances that can be irritating.
She could also be getting irritated vaginal skin from soap, laundry soap, dryer sheets, etc.
For the current pain, I would recommend sitting in warm water with epsom salts. This will be soothing and healing regardless of the cause.
In the future, using all cotton, organic pads will probably help.
If she continues with pain when wiping more than a few days, then it would be best that she see a doctor for an exam.