Regarding the "why is he repeating the questions so much?" posts, this is an extremely common tactic for finding out whether someone is lying. Keep asking the same question but word it as a new one and hit the person with the question at unexpected times. If the person is truly lying they'll blurt out the alibi one time and the truth the next. Cops, for instance, do it a ton when they pull over someone they think is driving slightly drunk. They sometimes innocuously ask "so where are you headed", and carry on a conversation for 5 minutes before asking "so where are you headed?" again and checking for inconsistencies.
She's already proved she has lied before multiple times. The repeated questioning is to find out if there are any other lies she's told.