I am a new horse owner. 36 years old and the only horse experience I have began within the past two years. My horse was given to me by my MIL who has thirty plus years of experience. Twice now, during her heat, my mare has acted up in the round pen - showing complete disrespect and refusing to come to me. She is completely obstinate running and running until she is dripping with sweat - tossing her head and turning out to the fence! My MIL is concerned that she is worked too hard when she has this kind of behavior and I refuse to let her behave that way because she knows better! Mind you the longest we have carried on in this situation is 45 minutes. The first time she did this, I literally had to leave her there - run to the grocery store and return in an hour. She then went willingly in. Last night I invited my spouse in the round pen to assist in cutting her off while she was running away from me and she then stopped almost immediately. So, I have two questions: When is a horse worked too hard, and am I wrong to continue my ground work when she is in heat?