My horse hates schooling?

I've been loaning a horse for a couple of weeks now, and i took her in the school for the first time yesterday. She's quite perky anyway when out hacking and stuff, but seems to lose her confidence when she is away from the owner's other two horses. She hadn't been schooled for about 3 years, i got told yesterday, so i was being quite cautious anyway. When she went in, she would walk around and stuff but she was just playing up. At one point she was just jumping up and down on the spot and throwing her head about and also tried to take off when i was lengthening one of my stirrup leathers. She doesn't really listen to my aids, when i ask for trot she tries to canter constantly (even when out hacking). She hadn't been rode that much before i got her either and she's a 10y/o ex-racehorse (TB). I was thinking about lunging her, but i'm not sure if i can and don't think they have a lunge line. Any suggestions to quieten her down a bit?