hi you didnt tell whether she is having fever
or not anyway it seems to be some allergic reaction
or it could be due to mosquitoes or some insect bite reaction.you can give her some anti allergic syp like phenergan
syp and keep her under observation .
if she is having fever it could be some viral or bacterial infection for that you would need to run some blood tests like CBC .in case of infection you have to give antibiotics,