Dad suspects that his daughter's good looking teacher might not be as popular as everyone thinks. When asked why, he responds:
Because various things are said about beautiful women
That's right. It's said that only beautiful women are cheeky.
Dad then seems to get angry and asks mum how she would know such a thing.
I think my translation of mum's sentence must be wrong. I'm not understanding the 美人ってだけで part. At first I assumed this was equivalent to 美人はだけで. But I think if you use は and だけ together then it must be だけは and not はだけ, so I guess the same is true with って?
Irrespective of that I don't see how translating だけ as 'only' makes any sense here. Nor, why dad would get angry at the comment.