Is My Chihuahua A Purebred?

[loves_it09]

I got my chi a couple months ago, shes now alot bigger than what she was. when i got her from a breeder they said she was purebred but now that shes older ppl ask me if she is mixed. So im just wondering if anyone can tell me if shes purebred or if shes mixed with anything. shes about 7 months old now and her ears are just starting to go up. Heres a pic of her.....

[dk1924]

She is very cute, but to me she looks mixed, not sure what though

[audrey23]

She really looks a lot like a rat terrier mix to me.
Did the breeder offer papers or show you the parents?? I'm always hesitant around breeders who won't disclose that information; especially if they're not even AKC registered as that usually means they're a backyard breeder, IMO.
Other than the breeder 'telling you' she was a purebred, what did she/he do to back that up???