And this is why I'll never own a mare again... My 2 old mares were horrible when they were in season. My last girl was the most loving sweet mare ever with impeccable manners, until she came into season when she would corner you, double barrel you in the stable, bite you as you walked past, jump out her field to get to the geldings etc. She was HORRIBLE. I gave her Oestress and it helped a lot, I also put her out with my gelding who quite honestly couldn't give a monkey's when there's a mare next to him squirting, she got bored when he wasn't paying her any attention - he was more interested in his sheep friends that were out with them.
I'd personally give her a hormonal supplement (Agnus Castus is pretty good) and push her about rather than her pushing you about. Not being aggressive - just putting her in her place by being assertive, keep walking towards her, take a schooling whip just to tap across her chest if she runs at you and just not give her the chance, I'd probably get a trainer in to help if she's your first mare as well.