see her leave/leaving

Usually, we'd say, "I didn't see her leave", but "leaving" is also correct", as in:

I didn't see her doing that.

I didn't see her cooking anything, but suddenly, there's food!

I didn't notice her reading a book while we were there.

I didn't see her leaving because I was talking to you.

I didn't see her taking your phone number.

etc.

Many thanks, Mame.