In some areas, the warm up ring has a "heads up" rule. You let others know where you are going by yelling that and the line or jump that you are taking.
If they are warming up on the flat for dressage, Your daughter may have to assert herself by asking him if he wants inside or outside and to let her know and not to cut her off. If she's not comfortable with thAt, you may need to do it. If you have a trainer, Or know one, Ask them to do it. Something to try: maybe talk to him on the ground about it, With others around so that you can stay calm and he has to be calm also as there are witnesses.
My dad once got in a trainers face... Not recommending that, but 25 years ago I almost got hurt b/c she had her student jump the same jump I had called. It was not good.