A little history:
I was hired onto this team a few years ago. The subteam I'm on has several people: the project lead (Jim), the co-worker I'm asking about (let's call her Mary), and others including me. We all report to the team lead (Tom), and most of the team works remotely, including Mary, though she commutes in to the office from time to time.
When I joined the company, they had no open offices in the area where most of the team works, so I was placed in another building. I told Tom I'd like to be moved to the team's office area, and a month later I got a notification from HR that on Monday at 4pm I was to move to a specific office in that wing. I checked, and it was Mary's office -- one of the nicest non-manager offices in that wing.
Assuming that she was simply moving to a different office (or perhaps that she had been told that she couldn't have the office anymore, since she telecommuted most of the time and offices were becoming scarce), I dutifully started moving my things at 4pm on Monday. Mary was still in the office, so I stacked my things outside the office door after a "hello" and a smile. I didn't ask or comment on the situation for fear of offending her, since the only communication I had received from anyone about this was from HR (and a quick email from Tom making sure I'd seen the email from HR).
Mary had always been friendly, so I was surprised and confused when she never smiled or greeted me again after that, not even when I said "hello". Work-related communications became stilted, and she never participated in any discussions I initiated. I mentioned this to Tom confidentially, as I was new on the team and wanted to solicit his advice. He said he'd "take care of it" but I never heard back from him and I didn't want to bring it up again.
Becoming increasingly frustrated, several months later I asked Mary if I could speak with her, and then asked why she doesn't speak with me. Her reply: "You are rude! I gave you my office because you needed it. You never said 'thank you'. You even put your things outside of my office before the end of the day." I tried to explain that I didn't know that and had been trying to avoid offending her, but she left in a huff.
Trying to make up for my offense, I left a gift bag in her inbox in the break area with some small, nice, appropriate gifts and a thank-you card. I never heard back. She still never speaks to me and avoids me as much as possible.
Is there anything I can do/say at this point to pursue an amicable, professional working relationship with Mary? I have no idea what she wants from me... At the minimum, I want to diffuse tension enough that we can discuss our work.
Co-worker gave me her office, I didn't say anything since I didn't know it was given and didn't want to offend, she was offended that I didn't say "thank you" and now doesn't ever speak to me. As a result, professional collaboration suffers.
It might help to also say: I have Aspergers.