I did tonight. I struggle with sunk costs, but I think I finally realized that I had probably been trying to too hard to make it work. We weren't seeing eye to eye, and I don't think it we ever would, unless she was able to decide definitely that I was what she wanted.
Dale Carnegie says that we need to put a stop loss order on our worries. In stocks, a stop loss order is when you say, "When this stock loses this much, sell it." That way you minimize losses. We need to do the same things with our worries. We need to say, "This is worth this much worry, and no more."
So I did that today. I told her she had my number and if she did end up making up her mind, she could call and maybe I would still be at a point to revisit it, but I'm moving on. She told me she'd see me around, but I don't know that she will. I don't plan to call, write, or visit. This train's leaving the station. I think it was the right thing to do.