Help!!!!!!!!!!

O.K. guys any help would be welcomed. We have been struggeling with Bella over playing in her bathroom sink. For the last few months, she has been bringing water into her room so she can have tea parties and what ever else and we keep telling her that she can not take the water into her room. Well, then I started finding glasses of water under her bed. It doesn't matter if we give her sippy cups with water before bed, it's not about that. She is deliberately disobeying and lying about it to us. Everyday she promises she won't make a mess and then I go into her bathroom and find her cups all over the sink and floor with water in them. Every day I step in puddles of water in her room or on the bathroom floor. She takes all the kitchen toys and fills them up and even if I hide all the cups, she somehow finds more. OK, so my master plan was to turn the water off to her sink and make her use hand sanitizer instead of soap and water and I thought I was so brilliant coming up with this idea, but boy was I wrong. It appears my 4-year old is smarter than me. This is what happens. Bella tells Aaron when he's upstairs, "Daddy I need a drink of water" and Aaron says, "OK, you need to leave the room and I will get you some". Bella say's " Dad, I know how you can turn the water on - you just follow the pipes behind the sink where there is a knob and turn the water on" and she goes behind the pedestal sink and tuns the knob to get the water turned back on! Aaron said "how did you figure that one out?" and She said "because I am very smart". Hmmmmmmmmmmmmmmm!
Bella is usually my good and obediant child. I hardley ever have issues with her, but on this particular issue, we cannot win. Any suggestions? Right now she's grounded from her room and has to sleep downstairs in the spare bedroom, but she's right next to another bathroom, so I don't know what to do. Please leave comments if you have any grand ideas. Thanks guys!