I'd also check out your trailer throroughly to make sure she's not telling you the floor needs work or that there's an electrical short somewhere.

The other thing to think about is how you drive with her once she's in there. Take a test drive with a bucket of water in the back. See how much water you have left in there once you reach your destination.

As for getting her in the trailer again safely, first make sure she leads with you well and moves away from pressure when asked every time even if the trailer's not there. You need to have that foundation there before you can implement it while loading. Once it's there, take your time, even if you have to spend some time with the trailer parked in a grassy spot allowing her to graze on the lead with you near it. Fear is probably the hardest thing for a trainer to deal with, so I sympathize.