My baby had chicken pox at abt 3 1/2 months old. He got it from my husband.
If it would happen, the chicken pox would look the same as your daughter's.
It was a very tough experience for my baby. He lost appetite and felt very uncomfortable. His doctor gave him some medicine (some said it helps and some said it won't). He became very skinny since then (he was pretty big before).
Did yr daughter touch yr boy? It would definitely very contigious by touching. the virus itself will be spreaded out by air too but not as easily as by touching.