I actually agree with Serpentine here. I daresay she just had other things taking priority in her mind.

I don't get it. Why should it be a Big Deal(tm) if someone likes you if you're happy with your current state of relationship? Unless it pings as creepy (thus feeling kind of threatening) or something really unexpected or unless I was interested back, I daresay I'd probably not quite remember things like that either. I would think that this lady heard it, acknowledged it, didn't find it especially emotional a revelation in any way, and thus it went out of her mind. I would hazard a guess that she's not interested. But nor is she creeped out by it, nor does she find it awkward or unexpected. It kind of speaks for her preferring to stay friends than anything else, at least now.

Studies (that I honestly can't quote, I'd have to look for them again) seem to suggest that people remember things better when they had some sort of emotional reaction to it (and that's why negative things stick to one's mind like leeches!). I know I've seen evidence of that in people I interact with (someone I know will not remember having watched a show episode... unless there was something that really struck an emotional chord, for example), and in myself. So my guess is she wasn't surprised, nor was she finding it creepy or awkward, nor was she interested back. Certainly I'm not going to call her a sociopath.