I used to always drink from my sink at night because I was too lazy to go downstairs.
If you were too lazy, why didn't you just go back to sleep?
I actually wanted my girlfriend to stop me from doing it. Instead she ended up drinking with me.
If you get really thirsty at night, why don't you get a glass and pitcher of water set up by your bed the night before? It's better than having to go downstairs or drink from the sink.
Maybe next time I will.
That sounds like a good idea. It's probably not safe to drink from a sink and you shouldn't rely on your girlfriend to change your behavior or to do things for you. Maybe you can develop good hydration habits together.