AITA for blowing up on my son's girlfriend?

My husband thinks I'm in the right, but my niece helped me make this post on here to see what other people think.

I (52f) have three sons ages ranging from 13 to 20. My oldest son (20m) has a girlfriend (19f) that hands around our house a lot... It's a really small house and doesn't have a lot of space. She's a nice girl but gets on my nerves sometimes because she's always over. I really don't think she's right for my son, either. Our tapwater has a weird aftertaste so I order gallon water bottles and use them to refill a big glass bowl with a tap.

It is not cheap to get water and other groceries delivered, so I tell my sons, husband, and the girlfriend to be courteous of the other people who live here and not use up the water, as it runs out fast in our big household.

Yesterday, I caught her filling up her big metal water bottle with the jug water, and I calmly told her that other people live here, too, and she shouldn't hog the water all to herself. She was rather short with me and said something along the lines of: "Actually, this water bottle is big enough to hold all the water someone should be drinking in a day. I'm not hogging water, I'm just trying to stay hydrated."

I found her tone to be disrespectful and ordered her to leave. She scoffed and went back to my son's room. That's when I really got frustrated. I opened their door and told her she has to leave. My son got really angry with me and told me that my girlfriend didn't do anything wrong and why is it a crime for her to drink water? I explained that I order this water for our family to use, not leeches who hang around all day rent-free. My son's girlfriend got a little teary eyed and left the room and out the front door without saying anything.

My son told me that I was a major asshole and should have just minded my business. I think she's just wasteful and a brat. AITA?