Yes, your kiddo has graduated long ago from baby talks and is a full fledged speaker now. Hence, her pronunciation needs to be more correct now. It is indeed very important to have correct pronunciation at the age of five! As a parent you must understand that these are the formative years of any child. Anything learned at this age stays with the kid all through her life. So you must ensure that whatever the child learns, she learns it properly.
What you need to know
Incorrect pronunciation is a common problem among kids of this age. They are still at a phase where baby talks do the rounds. Kids as a result get away with a lot of mispronunciation on the pretext of baby talks and age. But this is not correct. A good and correct pronunciation not only is a good thing to learn, but also shows the child’s dexterity and command over a language. It often happens that a child who is not corrected at this age goes on to use mispronounced words all her life, which causes her huge embarrassment.
What you can do
So, as a parent you must ensure that the child must try to speak the word correctly, no matter what. It also may happen that the wrong pronunciation is the result of some speech disorder. In such cases, detect the problem and don't hesitate to seek help from a specialist. Correction at the earliest is the key. A child reaches out to the world through his language and speech. It is thus absolutely imperative that as parents you hone this skill as much as possible, and give your child confident and fluent communication.