She's your mother. I wouldn't expect her to be objective, LOL. Do you think your sisters are pretty? There's no need to answer, you probably can't be objective either.
My wife thinks are kids are handsome, as do I.
My father could be disturbingly blunt about such matters. ;<)
One of my brothers got the genetic fluke of flax colored hair and thick, jet-black eyebrows. Since he's 6'4" and wide as a truck nobody mentions it, but our mom definitely thinks he's handsome.
I do think both my sisters are pretty. I also know that one of them can eat a quarter of her weight of pancakes in half an hour and the other can fart the alphabet...At will. Any of their potential suitors of whom I strongly disapprove will be informed of these talents post haste. I'll plead big brother immunity and skip town for a while. All in a day's work. :)