Is she actually stuttering, or is she just having trouble putting her thoughts together? It is very common around age 2-3 for kids to have trouble getting their thoughts out. A typical conversation with my daughter would be:
Her: Mommy?"
Me: "Yes?"
Her: " I, I , I...uh"
Me: "What do you want to say?"
Her "I,uh, I want, uh....want to,.."
<time passes>
Her:"Mommy, I uh, want to, hmmmm... I , Mommy, want to...."
Me: "Try again."
Her: "Mommy, I, uh, need you to, uh, open this for me."
It's not really stuttering so much as a disconnect between being able to compose a "grown-up" sentence to match the speed of their thinking. They are too distracted to complete a thought. Suddenly, they are preschoolers having pretty complex thoughts but their language hasn't really caught up.
Try to think about the situations she does this - can she play and talk to herself with no problem, but when she is trying to express somthing to you, then she has trouble?
If it is genuinly a stutter, where she is getting stuck on the pronounciation or completion of a word, then I woudl not wait a second to get intervention. Those kind fo things don't get better on their own.