Hi Sabbi,
If the bite is just itchy and blotchy you could try some anti-histamine cream or oral medicine (or both) if your little girl is the appropriate age. This will help to prevent her scratching it and possibly introducing an infection. If however the bite is infected (quite swollen, hard, hot, angry red etc) then you may need to treat with an antibiotic medication and that would require a prescription. Either way try to make sure that she doesn’t scratch, pick or squeeze the bite and you can bathe in some warm water with antiseptic to keep it clean.
I hope that helps,
Regards