Thanks for the query,
She might have developed acute urticaria
It is an allergic condition.
Anything including food, cloth, change in climate, pollens etc can cause urticaria.
You need to find out the cause.
Treatment can be with oral anti histamines
Steroids like prednisolone
are also helpful but cannot be used for long.
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.