Thanks for the query,
It cannot be chicken pox
Chicken pox spreads very rapidly throughout the body.
she might have developed an allergic reaction
The cause can be varying,
It can be due to an insect bite or any thing taken orally or inhaled.
Ask her to Apply a steroid lotion like desonide
Also give her an antihistamine tablet.
This will give her some relief.
Please meet a dermatologist
for exact diagnosis.
Let me know if you have any other doubt.
you can ask a direct question to me on this forum, following the below link.
Wishing you a good health.