Does she feel or look overweight (can you feel/see her ribs?) I can't tell because of that very pretty dress she is wearing.
Kaos was around 2.5 lbs at that age but all yorkies are different. (He is only 4.5lb full grown.) Some yorkies are simply larger than others. (+10lbs at adult size) Has she been to the vet? If she checked out ok I wouldn't worry. I'm no expert though, maybe some of the more experienced YT mommy's will chime in.
P.S.
She's a cutie!!!
