I would hazard the guess that they are bug bites of some sort. Spider bites are usually a few smaller bites in a group, and sometimes they can be a single and can pretty big and irritated. I've never seen a recluse bite, but I've heard they get ugly fast,*as well as bed bug bites) so if it's been 3 days or so then that's not a concern.
Could be mosquito bites, if she sleeps with her arms out from under the covers.
If she is itching you can use Benadryl cream on them and itch goes away pretty fast.
I'm thinking if she had chicken pox that the ones she has would already be blistering, and she would have LOADS more on her torso and body creases. Measles are probably also out, unless she hasn't gotten her immunizations yet.
One suggestion, strip her bed down and wash all the bedclothes. including blankets. while that stuff is washinf flip the mattress and look for spider webs, and such. Clear all that out, and you should be good to go.