You will probably find that this baby speech is rather cute, but do not imitate your child’s speech or even mention it to your child - this could result in your child sticking to this way of speaking. It is not a good idea to correct your child when she speaks this way either - it could make her become more self-conscious than she already is. Simply talk properly to your child and be a good role model.
Lisping occurs when your child pushes her tongue forward instead of letting it lie behind the teeth when forming the s sound. As they get older and their speech abilities progress, most children outgrow lisping naturally.