Thank you for your query,
This fluid filled skin lesions may be due to chicken pox
or some other viral illness and needs examination by a Pediatrician
to advise appropriate medication.
Bitind nails and skin of fingers and thumbs is a sign of tension releasing phenomenon and try to reduce her day time anxiety
by giving emotional support and by telling stories at bedtime.
Still the biting persists, you can apply some allowed bitter cream or liquids on nails and fingers as a method of aversion therapy
after consulting your Pediatrician.
Hope I have answered your query.