I too think an email would be fine. I sent mine flowers when I left the UK, as she had been a great source of support and I had really appreciated it. I did call her on one occasion after I left and although it was really nice to talk to her it did remind me how much I missed her so I don't think I will do that again, or not for a while at least.

I would think that Ts probably like being appreciated, just as we all do. I'm glad it was such a help to you.