S.S.
just one is probably a canker sore though I would look in her mouth for the next few days to see if more pops up. my son had a version of the handfootmouth and he had a whole bunch of canker sores when he had it. couldn't eat at all (which was so sad bc he loves to eat!). just keep an eye on it. she could just be tired (which makes canker sores appear)