My mother bred one of her mares a couple years ago, and she had a lot of hormonal/behavioral... things. It was rarely a problem when she was interacting with people, but at one point a couple of my dogs got through the gate and followed me into the pasture while I was catching Sage, and Strawberry attacked the dog and trampled her. Jesse died in my arms later that night due to internal bleeding.
I'm convinced that that was entirely due to hormones, as that mare had been around dogs with no incident or problem since the day she was born, and Jesse hadn't done anything to provoke her. And there hasn't been any problem since.
Strawberry was only a month or so pregnant, so it's not out of the question that your mare is having hormonal problems, too. All I can say is be sympathetic, but also make sure that you're not allowing bad or dangerous behavior when you're handling her.
The hills were bathed in moonlight, the shadows not so stark;
Silver light reflected off his brown hide as he held me in the dark
– I love you, Mudpie!