How to deal with a new richer co worker?

I have been working in this office for 6 months, and I was the only female around here untill a new girl joined recently, and she is richer than I am and her dad owns a company which is the biggest client to our office, she is not that serious about working, I guess she is still new so she will be that way untill she gets used to the work.

My problem is that she asked that her office be with me since I am the only female, so we decided to share desk, and she just keeps on chatting with me which has been distracting, and bringing her friends over to the office just to visit her, and they spend the whole day in my office distracting me more from my tasks, I feel that she is really excited to be working for the first time, but since she came I wasn’t really able to do as much as before which isn’t good for me.
The other problem is that she keeps on requesting me to go out with her for lunch, and she insists in expensive resturants, she is the one who pays for it, but I don’t want to owe anybody that much, today I got my own lunch with me from some where else, and she asked me to just go out with her, and I can eat my lunch outside, then she asked me to make an order, when I told her about my lunch, she said that she would pay for it and I can pay her back and I can have my lunch latter.
I know I could sound silly, but I haven’t been working for a long time so I am not sure how to approach her about this?
I am also the type of person who trys to avoid confrontations and arguments alot so that is also a problem in me.

If anyone has any good advise, I would be happy to hear it from you.