Given that this has been your first relationship, that means you are going to be learning and when it comes to relationships each person we have a relationship with is going to have their own way of interacting and a lot of times others are actually learning too. In all honesty, if I had a boyfriend and introduced him to a friend of mine and then this friend began to constantly interact with him in the manner you shared, I would begin to question this friends ability to respect MY boundaries. This friend of yours is showing that she doesn't "know" that her constantly interacting with your new boyfriend was getting intrusive. I think that all this new technology we have has presented some new challenges when it comes to respecting boundaries. This is especially true for younger individuals who tend to spend a lot of time interacting with texting and posting on facebook. The younger population has been gradually exposed to thinking it's ok to interact and collect friends with all this new technology and because others can see how much they interact with certain individuals, it's easier to see that it may be too excessive where the friend isn't recognizing that because they tend to be drawn to anyone that engages them.

If what this friend did was intrusive to you, given that she is your friend you should tell her that when you have a boyfriend you would prefer she limit her interactions with YOUR boyfriend interest. And you can also let whatever boyfriend know that you don't want to isolate him but it does bother you when you are engaging in a relationship with him and he ends up constantly chatting it up with a friend of yours as though his relationship is more with your friend than you.

If this friend of yours engages in ways that bother you then the next time don't introduce her to the guy you would rather have some privacy with while you interact with him to see if he is a good match for you.