M.P.
It sounds like you are pretty tuned in to your daughter and what might be going on under the surface. Lying is a tricky issue. Our kids tell us what we want to hear because they want to please us and don't want us to be angry. Or it's something they don't even see as lying, such as yes I brushed my teeth (and they are remembering last night when they did brush their teeth.)
I find it helpful to take some of the seriousness out of it. When children see we have a sense of humor and can understand them they feel trusting of us with the hard things in life. (This is especially beneficial once our children reach the teen years. Teens talk and share more with parents when they feel that unconditional love.)
Have you tried responding to the lying with a playful touch? For example, she says, "yes, I brushed my teeth." and you know she didn't, so you smile and say warmly, "You did? Oh, please let me smell your minty-fresh breath then!" If she let's you, you might respond with a perplexed,"Hmm, your breath smells more like breakfast than toothpaste. Are you SUUUUURRRE you brushed your teeth? Maybe we should try again."
She may not let you smell and try to get you to chase her instead. This is good too, it lets your daughter see that you love her and want to connect with her. It adds warmth and play to the relationship. You may notice a little increase in the lying because your daughter will love the attention, however, I have found this isn't a negative. because as my daughter sees my love pouring out for her no matter what, the need to lie starts to disappear. She sees she can trust me and tell me anything. She knows I'm not going to fly off the handle at her or treat her coldly and disapprovingly.
Here's a fantastic article that talks about answering children's core questions: http://www.handinhandparenting.org/news/36/64/Answering-C...
I hope this helps! Parenting is a tough job, but it can be fun too!