Why is she nervous on the trailer?
I think that's the question you should answer, whether or not you ever plan on taking her anywhere once she is at your home.
I purchased Clinton Anderson's trailer loading DVD about a month ago and it is amazing. I highly recommend it. And the DVD is not just about getting your horse on the trailer; it's about everything else, including horses that are nervous on the trailer.
How does she load up? Does she leap into the trailer? (not necesarily a good thing, because that means she's rushing) Does she get out of that trailer as fast as possible once the door is opened? Does she paw and move around alot when on the trailer?
Basically, you need to make this trailer a place of rest for her. The trailer should be a good place to be.
Are you sure her ground manner are perfect? Can you move her feet and any part of her body (shoulders, hindquaters, etc) in any direction at any time? Does she crowd you or run over you when frightened of something? You'll need to work on those things first before working on trailer work.
It sounds like you have a few weeks to work on this, so you should take the time and do that. If her previous owner allows, get over there and work with her on the trailer loading.
You should be able to load her foot by foot. That means she doesn't rush to get into the trailer. She should put a foot in, or back a foot off whenever you say.
And in order to make the trailer a happy restful place (for those who are nervous on the trailer), is you need to make her WORK outside the trailer, and then get to rest inside the trailer. WORK can be lunging circles, changing direction frequently (as that's harder, and it keeps the horse focused on you). Eventually, as you are WORKING her, she'll head for the trailer on her own because she's thinking "Silly human. All I have to do is jump in this trailer and he makes me stop working!". And that's exactly what you want the horse to think.
Do this in the weeks ahead BEFORE you need to move her to your place. This will help her to see that the trailer means rest and it's a good place to be, and no need to be nervous in it.
You can feed her as a treat if you want in the trailer, but that's not entirely going to take her nervousness away.
∞•*˚ Βгįťţαňγ ˚*•∞
It is not enough to know how to ride; one must know how to fall.