I would say "demand that she leave the house". It is the mandative subjunctive.
Student or Learner
Can you use "demand" like "ask" in a sentence like "He demanded her to leave the house" or does it have to be "He demanded that she left the house" / "He demanded of her to leave the house"?
'Demand' is much stronger than 'ask'.
I'd say 'He demanded that she left the house'.
The subjunctive is little used in BE. It has not been taught in British schools for decades.
We seem to manage OK without it.