You can either tie her in the back of the trailer with her facing the back or else kinda tie her at a slant. She might find it easier to stand that way, since it distributes her weight more evenly and she can prepare for stops better. I would do a quick release knot, and tie it just enough so she can look around a little but not enough to get tangled in/get a hoof through if she gets scared. Good luck!
Shaneequah, 1998 gaited Bashkir CurlyxArab mare
Treyue, 1999 3-gaited Icelandic gelding
Loki, 2001-2015 Icelandic gelding