There is a real problem here and it's not clear from what you say what that problem is.
Your fiancé does not feel safe with you. She is rebelling against you like a teenager rebelling against her parents. She has problems with authority and is placing you in the role of angry father, even when you don't want to be there.
There ARE Obligations
I'm not sure there is anything YOU can do. This is her trip. She's afraid of the close proximity of marriage -- how can you make her feel like there's no obligations, when there clearly ARE obligations?
I would go to counseling with her...fast.
There are Deep Emotional Issues Here
These are deep emotional issues that are coming out in your relationship, and your "desperation" will not help. You will find yourself doing things you resent, or getting angry, or feeling desperate. You two need a safe place to talk this through, and to come up with a strategy for solving the problem, to make her feel better.
Many times people don't know why they feel the way they do. They take those unexplained feelings and assume that they are reality, when in fact, they are just feelings. It's okay to feel, but not all feelings are reflective of anything real.
Her feelings here are not very rational if you are assuring that you are not putting strings on her. So you two need a way to deal with these feelings so you both feel safe and closer. It's definitely possible, but you have to work together...and I think a professional counselor can really help out here.