Dear S.,
A child therapist told me that at this age, children aren't concsiously lying, sometimes it's a matter of simply stating what they WISH were true. Your daughter knows she got water on the floor and she WISHES she hadn't or WISHES someone else did it. And it's highly likely she WISHED she didn't have to clean it up.
Their little imaginations can really take off at about this time and that is not a bad thing, but you have to help them discern what is real and true and what is make believe.
Both of my kids have vivid imaginations and what I did when they were little was have story time...I had a notebook and as they told their story, I would write it down for them and read it back when they were done. I read to them a lot, and sometimes, they wanted to read their own stories instead of another book before bed, etc. If they went off on a tangent when I asked how a toy got broken or something, I would say we could save that story for the notebook, but for now, I wanted to know what REALLY happened, did they step on it, sit on it, throw it?
We've all heard of Mr. Nobody. It's fairly typical for kids to say, "I didn't do it. It wasn't me."
We want our kids to be honest and know the difference between the truth and lying, but at 3, the concept of being dishonest is hard for them to fathom. Jack and the Beanstalk is a great story, but it never really happened. There are no magic beans, there are no giants, there are no geese that lay golden eggs. There is no such person as Peter the Pumpkin eater. There are no old women living in a shoe.
These are all things kids are trying to grasp and I personally think that having a great imagination is a sign of intelligence.
I would relax a little bit and not focus so much on the principal of lying just yet. Let's face it, we moms know when we're getting hoodwinked. Our kids knowing that we know goes a long way in helping them understand that just saying something to us doesn't make it so. You know who got water on the bathroom floor...no point in asking her who did it. No point in asking her why she did it because that's a pretty abstract situation as well. How it happened....were you brushing your teeth, were you bathing your doll in the sink, were you playing in the toilet?....Regardless, you know she did it. She knows she did it. She can clean it up and save her story for another time.
Try the story notebook. It gives you a chance to have a window into their imaginations and I still have the stories my kids made up when they were little. We get them out every now and then and have the best time laughing and reading them.
Hang in there!