Re: Excitable horses :)
well, is she the same over just poles? I had to go back to just walking and halting standing over a single pole on the ground 10 times a riding session with my first little mare. she was a welshie/anglo arab, 13 too at the time, and jumped like a loon! I took her right back to halting over a single pole, then walking over 2 poles, then 3, then 4, then trotting over one, then two, then three, then four... you get the picture! Only progress to more poles when you can do them quietly and in a controlled manner. If she gets wound up, come straight back to walk and do something completely different until she calms down - try some leg yield or shoulder in, for example.
Also, instead of plonking her at speed at an individual fence, try gridwork with her - lots of little crosses means she has to slow down and think about what she's doing.
It took me months, but we got my wee pony up to jumping quite happily round 2ft 6 :)