I don't think Amy can be ruled out as a trap even on the grounds of how she is - I think Amy is a normal person (well, of a type of character that would fit being a companion regardless) who has grown up in a very, very strange environment and it very probably totally honest and innocent.

I think, for me, there is a question of why her environment was strange - was it by someone (the missing aunt) "grooming" her as a trap or pure chance (her growing up in a house where the outside is bigger than the inside and what that entails).

And I don't know which