You don't enter out of the building. Like you don't tuck in your shirt to your pants but "You tuck your shirt to your pants." You don't tuck something out.
oh no~~ my english is so bad !!! so the answer is "she entered the building"? how come?
I'd say just 'entered' is okay, as is 'entered into', but not just 'in'.
To enter means to go in, so "enter in" is redundant.