I am a speech pathologist, and I disagree with George. If everyone brought every child who stutters the moment stuttering begins, it would be a mess. The fact is, most kids stutter at some point. The general rule of thumb is that if they are stuttering consistently for 6 months, then you could consider taking them to an SLP. That said, the most recent literature review I read said up to 18 months could be normal and it is completely OK to take a "wait and see" approach for 18 months. The reason 75% of kids who stutter recover is because often it is a temporary thing. The fact that she is a girl is also in her favor.
When she stutters, what does it sound like? Whole words being repeated? Sounds being repeated? Phrases being repeated? Sounds being prolonged? Silent blocks or periods of being stuck?
True stuttering is one of three things: part word repetitions (ba-ba- ball), prolongations ( I ssssssssssssaw you yesterday), and blocks (silent block where no air is coming out and child appears stuck or frozen). Word repetitions and phrase repetitions are not stuttering.
Also, I will say that both me and my husband are practicing speech language pathologists and our son really threw us for a loop. He began stuttering so severely that we were both just floored. He stuttered so much that when he got stuck in a part word rep, his jaw would keep moving saying the sound over and over until he actually raised his hand up to his jaw and physically stopped the movement. It made me panic inside, but we stayed as cool as we could about it. One major thing a family can do to help is decrease time pressure. Try not to make your child feel hurried, and if they talk to you, stop what you are doing if possible and make eye contact to show you are listening. Don't tell them to slow down or "think about what they are saying." Just give them time and show you are listening. This helps decrease the issue a lot. It is a passive intervention you can try without labeling your child as a stutterer and directly addressing it. We included our 6 yr old daughter in this as well. She did not directly mention it to him, but when cued, she would back off, not interrupt and let him finish his thought.
In my son's case, he became fluent and we breathed a sigh of relief. He was fluent for many months, and then it started again. It freaked me out, but not as much the second time around. I have noticed that there tends to be a language explosion right around the time of these episodes. When he becomes fluent, it is striking to me how his sentences have become longer, more complex, more "big boy" sounding.
Please feel free to PM me if you have questions or additional info you want to share. I am happy to help.