T.B.
Hi S.!
I am a speech therapist and a mom so I understand your concern totally. What I will tell you is that children often go through what is called "normal childhood dysfluency" and it usually occurs between the ages of 2 and 5 and fades away. Children may occasionally repeat sounds or syllables when they are excited or tired (not to mention they are trying to take in all of our fancy adult "lingo" and speech patterns :-) Being that I don't know your family history (for example I don't know if anyone else stutters etc...) I obviously will never attempt to diagnose her or anyone elses child via the internet but I will say this, try to avoid ANY show of disapproval (through facial expression) or say things like "slow down" or "take your time". Research has shown that it may make the child more self-concious and we want her to continue to talking freely . Always look directly at her in those moments and continue to postively encourage her fluent speech. If you are still concerned about her speech by age 3, I would recommend for your peace of mind that you have a speech therapist evaluate her. Only they can diagnose what is called "true" stuttering.
Here is a fantastic link that should give more insight into this topic ; http://www.med.umich.edu/1libr/pa/pa_bstutter_hhg.htm
I hope this was helpful!