My brothers girlfriend keeps leaving in the middle of the night and it's making me sleep deprived. What could I do in this situation?

My brother 25 (turning 26) and my brothers girlfriend 26 is leaving during the midnight all the time. My brothers girlfriend always comes over at 6pm or 9pm and she always leaves at midnight and it's waking my mum and I up. We have tried talking to her really nicely about the situation but she's still leaving at 1am but my mum and I liturally have work and school the next day and it's honestly making us sleep deprived because of it.

Is there any advice anyone can give me on what I could do?

Ps. I also don't have contact with my brothers girlfriends parents as I don't know who they are.
My brothers girlfriend keeps leaving in the middle of the night and it's making me sleep deprived. What could I do in this situation?
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