my son gets allergic reations to mosquito bites and they swell up like that and he has to be on antibiotics too. also likje mentioned before take a pen and draw around the circle so if it is getting bigger you know and also if it goes otside the first ring draw another one and put a time on it and keep doing it everytime it goes outside the lines. i hope she feels better soon i know how miserable my son is when he gets those too. he swells up just like that one time it looked like he had a baseball in his arm
it could be a spider bite or any of the other bites but i just wanted to let you know that allergic reactions to mosquito's look like that too.