My DD did the same thing all of a sudden at about the same age hun, we just took it really easy with her and never interrupted to finish her sentence etc. and she did grow out of it, from memory it took a few months and would come and go. If you find that she is getting worse, or more frustrated by it all the time it might be worth seeing a speech pathologist, you may find she only needs to go a few times to get some strategies as it could be her brain moving faster than her mouth can go which is what we found with Iz and as I said she's grown out of it now at 4.5