Welcome!
Go ahead and take her to the vet just to have her checked for the usual stuff and see if she is underweight, as a previous post said, u can always take her back if necessary once you get the records.
As for the food issue maybe she is still a little sad about losing her previous owner, but I am sure she will warm up to your family in no time though! Maybe you can ask the previous owner's son and ask him if he knows what she was eating before. My dog was a picky eater at first but the vets best advice was "When she's hungry she'll eat," ..she did and now she'll eat just about anything we will give her (although her allergies keep her on a strict diet).
Congratulations on your new baby, she's a doll!
