Hello, teachers!
Are both natural and common?

1. Don't wake her up. Let her sleep more.
2. Don't wake her up. Leave her to sleep more.

Thank you very much.
They both sound fine.

You might want to consider 'for longer' instead of 'more'.
the right sentence would be
Don't wake her.Let her sleep some more.
Students: Are you brave enough to let our tutors analyse your pronunciation?
Thank you very much.
Enjoy the gorgeous fall sunshine!
 anita_a's reply was promoted to an answer.
Teachers: We supply a list of EFL job vacancies
It could be a British vs. American English difference. As an American, I would say let her sleep some more or let her sleep longer (not for longer), or just let her sleep.
I was thinking the same thing. I assumed "for longer" was a British way of saying it, because in the U.S., at least, we just say "sleep longer". Maybe Nona will give us a clue about this one.Emotion: smile