What Breed Is My Dog?

Can anyone tell me what breed my new puppy is? She was a stray until about 4 days ago, we took her in and she's just amazing! I cannot comprehend why anyone would let her out like that. She's about 8-10 weeks old, an incredibly smart pup, huge paws, fat belly, like a Lab, and she's very pretty. People are always asking what breed she is. I just say Lab mix. We won't know more until her first vet visit. Any ideas? One friend said Lab/Shepherd mix.