Lawyer vs. Exec Assistant

I started recently at a boutique law firm where out of 19 attorneys and staff, I am in the only woman in the office - with the exception of the Executive Assistant to the partner. Since day 1, she has been rude to me. I've tried to make small talk and be polite, offer to bring her coffee, etc., but she gives me the impression that she thinks there is not room for both of us. She's been with the firm for over 20 years, and I am also the first female attorney they have hired. For example, when she delivers our mail, she walks up to a desk and hands it to the male attorneys, but she barely gets in my office doorway and tosses it in the air and onto my desk. I don't even know what's going on here. We haven't had any negative interactions, except for the way she treats me. Any suggestions on how to approach this?