Look, she would rather you just had your schedule a little more organized, but if you must know, she will definitely shuffle some things around in order to spend time with you. If you realize you have the night off but she has drinks with her colleagues planned, she will figure out a way to get out of it in what seems like the blink of an eye.
Let's be clear, though, you can't be suddenly available at the last minute all the time. She has got a life outside of you. Have some consideration for her schedule and lock in your nights with her in advance. However, it's always nice to know that if your plans with other people are suddenly cancelled, she'll do everything she can to spend the time with you instead.