I remember reading that toddlers really do not know (or should I say GRASP) the difference between the truth and what they may want to believe. I think it is a phase and it will pass. My mom always told my son about the difference between "the truth" and "a story." Maybe at the dinner table, tell her about seeing a unicorn walking along the street or something like that and it will open up a discussion about truth vs. stories.
I know the moms on this site are experts on lots of things, but no one can be an expert on EVERYTHING! Here are some useful sites for your review about fibbing at the very tender age of "JUST TURNED 3":
www.parenting-ed.org Lying Behavior Before Age Three - Children May Not Be Aware They Are Lying
Before age three, your child is still acquiring very basic speech. She can understand much more than she can accurately express. She is only beginning to learn how to use her speech to cause events and to describe her thoughts and behaviors.
www.childrenshospital.org When confronted with a child who is lying, it is important to first remember the child's age and developmental stage. Children under the age of 3 do not lie on purpose. This age group does not understand what they are saying and instead are just experimenting with language and new found facts about the world. They might also lie to avoid punishment because they understand the consequences but have an undeveloped moral code.
Children from the ages of 3 to 7 often have problems separating the real world from fantasy. They might have imaginary playmates at this age and enjoy fairy tales and make-believe play. The lies told by this age group are mostly tales that they have made up, not intentional lies. By the age of 6 or 7, however, children understand what lying is, but will continue to cheat if able.
www2.scholastic.com At this age, wishes and imagination often get in the way of what is real. Sometimes a 3 year old will start to tell a story, and you will hear it get out of hand as he adds bits and pieces to fit the ideas in his head. Lies at this age might succeed, but 3 year olds are generally poor liars because they fail to lie appropriately. They do not consider that their listener will actually think about either the statement or their intention. As a result, they tend to lie at the wrong time or place, or neglect to think about other important facts, such as covering their tracks to conceal the deception.
By age 4, children know the difference between telling the truth and lying — and they know it's wrong to lie. So, generally, they're truthful, and when they're not it's obvious. But they also become more proficient at lying because they're more cognitively capable of taking into account the listener's belief of their statement.
M., there seems to be a consensus that BY AGE 4, kids are beginning to understand lying and are also being taught by parents how to engage in social lying. They can also lie to avoid unpleasant consequences.
They lie to get out of trouble, not to get into it," explains Susan Shapiro, Ph.D, MS,MS, RD, FADA, a clinical psychologist in Los Angeles who practices in child development. "Unlike adults, who will lie to impress and flatter, children will lie when they feel there are under a reward and punishment system.
Young children (ages 4-5) often make up stories and tell tall tales. This is normal activity because they enjoy hearing stories and making up stories for fun. These young children may blur the distinction between reality and fantasy. Tattletales are another method these children utilize but more self-serving: If they tell on their friends they may be looked upon as the more honest and trustworthy of the group.
As you can see, it is very unlikely that at 3 years and a few weeks, that she is doing this on purpose, or even grasps the concept of lying let alone the implications of lying.