"get in" vs "get on" vs "walk in" vs "get into" – the elevator

I'm writing a short story in third-person without being too formal. I've run into trouble when deciding which phrasal verb to use.

A woman is making her way to the elevator. There are two people in the elevator already, one is an old man and the other is a young boy. As she __________, she asks the young boy.

Options that I can think of.

gets in

gets on

walks in

gets into the elevator (this is wordy)

Which one works best?
Or, are there any other alternatives besides "enters"?