I agree this needs to be addressed properly now.
I want to give the feed a try first - the mare was perfectly behaved before this excess energy started to build. She didn't have any fight in her. Even if she thought about resisting, one tap with the whip sent her forward at a trot. She got put on an alfalfa mix and it was like I had a different horse. I know there are a lot of varied opinions on alfalfa, but I have talked to several Iberian nutritionists who have said to get her off it because they are efficient horses that don't need a 'hot' feed.
Before making any extreme decisions, I will see how she does back on a low energy grass feed and whether this changes it back to how it was.
I rode the mare everywhere for a month - alone, with buddies, to the riding club, busy streets, taught her to handle gates, etc. etc.
Only when we introduced the feed change did all this start.