I like
Carissa. My first impression of someone named
Carissa is a tall, mature girl with wavy blond hair.
I like
Caris too but I prefer
Carissa. Carysa wouldn't be too bad for a variation, but I still prefer
Carissa. I don't like any of them spelled with a k.
I don't think they would be strange for a mother and daughter. I know a mother and daughter named
Lorna and
Loren, and nobody thinks it is wired (although they do gwt called by each other's name occasionally.)