How to ask a co-worker to give you space without hurting her feelings?

I share a very small office with a co-worker.We both have long tables as our desk along with file cabinets and basically our own little space, which is fairly comfortable. Well, we also have a newer co-worker (Chiropractor) who has her own office that's bigger than ours. On her first day she wanted to sit in our office so she can get a better idea of how things work. So I pulled a chair from the hall into our office and sat it by my office mate desk. Now, 6 months later she sits in our office all day along, in between seeing the patients. Not only does her conversation irritate the both of us (office mate replies more to her to show interest), she has negative energy and when we disagree or don't reply to her she tries to redirect her words to match ours and says whatever she can to try to fit into the conversation. She is also in the way. We have to constantly say "excuse me" and practically be bumping into each other. She is also very sensitive and hates sitting in her own office. I think she is starting to pick up on my vibe that she is becoming annoying and clingy. I have a feeling I am going to end up hurting her feelinsg but I don't want to. How should I ask her to sit in her own office sometimes without hurting her feelings? Any advice will be greatly appreciated...... : )