This may seem strange that a project manager would see enthusiastic and energetic self-starters as a problem. Well in general they aren’t, as long as they’re working to the agreed plan. They are a positive menace if they exceed the responsibilities of their project role. By straying outside the boundaries of their duties they run the risk of alienating other team members or client personnel.
Every horse no matter how spirited has to be bridled at all times. They only run when the rider says so.
The German army used to have a guideline on how to handle different types of officer: if you have an intelligent and energetic person promote them rapidly; if you have an intelligent but lazy officer keep him around for in a crisis he will be of use; if you have a stupid and lazy officer then use him to command a barracks or some other nonessential facility; if you have a stupid and energetic officer then SHOOT HIM, because he will cause no end of trouble.
Now I’m not suggesting the use of capital punishment on your projects, but I am suggesting that you do not let your team members go off on their own initiative until you know their skill and interpersonal capabilities. Relationships take time to build and can be destroyed in moments by the blundering of a well meaning but maladroit individual. Should you get someone like this assigned to you then them keep inside the team until you can control her, or ship her out to another project ASAP.