Not sure how big is the scale of your responsibility here

If I were you, someone is interested in my stuff and I know I can handle the situation, why not let her know more and let her take a part of it?
then you have less hands-on to do. It is like having another report or part-time right? Of cause you need to be in control of the general picture and only let her handle the part that you let her to take. The other part is to tighten your relationship with team leader.

If this is too strong a person, then you may need to protect your territory. talk with team leader to give her sth else to do, distract her with other stuff. Usually people want to get involved in multiple projects for security reasons. It is not that bad.