I think that the fact that we were out at school at all is the issue, not the fact that we were holding hands. I do hold hands with my friends (female), but when S and I are together, I'd venture to say it's pretty obvious that there's something other than just friendship going on. Add to that deep seated fears on L's part because all of her past relationships have ended with her partner (female) leaving her for a man, and you get one scared cookie. I've tried to be very aware of that, but I know that S and I moved too quickly at the beginning for her comfort, and when she expressed her feelings about that, I didn't respect them.
There's a whole lot going on in this situation, lots of background that's getting worked through and rehashed, but the main issue is that she feels like I don't care about her feelings or her boundaries -- which I do, an incredible amount, but I'm not very good at the reassurance part. And while I'm working to improve that, things keep getting mired in triggers for her and defensiveness for me. I'm being honest though, and I'm doing the best I can at the moment. I know these things take time, especially when they've started off in about the worst way possible.