Do you have a stock trailer rather than a two horse? You could put some feed into the front, corral her with some pannels and give her time. There is no other way without a seddative unless you have time to work with her.
If you do have time to work with her you could back the trailer up to the pen and work her. Just make sure you use the trailer as a safety and resting zone. Eventually she will realize the trailer is a good thing and you wont even have to touch her. Just close the middle gate after she has loaded a few times and feels comfortable and calm in the trailer. I would NOT use a two horse trailer on her first trip. I have actually had one jump half its body into the front of one while I was hauling it down the road before!!!