We had the same problem with a lady that used to board her horse at our barn. I ended up excersising her horse for her bacause she was too timid and the gelding was way smart and knew it. She ended up selling him. maybe you could work the horse for her before she got on and show her how to handle him and show how he good he could be under saddle? im not really sure. maybe she shud just get a gentleer horse