So this spring... we have ridden her occasionally over the winter, and this is not uncommon at all for her to go for a while without being ridden, and she is always perfect coming back into work. We go for a ride. I am on my other horse, and Lassie is being ridden by a novice friend. She bolts! As soon as you bring her to the lope, she's gone, just takes off. So my friend falls off, gets back on and lassie is still being a pain. When I ride her, she is a complete doll, when my dad rides her, again a complete doll, he even rides her without a bridle and saddle. Now when someone else rides her, she will bolt with them. I am a little lost as to what to do. I figured I could have friends over who I know could handle it, so when she tries it with them they can correct it, since she doesn't do it with me. I can't put beginner riders on her now, and I just don't understand why she is acting like this all of a sudden. I was thinking maybe some sort of pain, but if that was the case I would assume she would do that with me and my dad as well. Any ideas on the cause and way to fix this?
A picture of the sweet gone crazy thing