Because she felt too bad to turn you down outright (because she'd known you for a while or other reasons) and also felt that one date should be enough? I had one of those recently...I figured it out during the date that she didn't really give a sh*t. And looking back at her behavior leading up to it, the signs were all there. Kind of made me angry afterwards...like, it was as if she thought she was gracing me with her presence or something.
Most Helpful Girl
Can't speak for all girls, but I have done this (once) myself. We'd been chatting for ages, and getting on really well. But the majority of our talking was via text or Facebook. We were both flirting when talking in text, but that really wasn't there in real life. He asked me out, and at first I was genuinely really excited, but after a little bit of time on the date realized there was actually nothing there (on my side at least) Didn't want to leave after 5 minutes, but did feel pretty bad for carrying on the date without being interested...
Know this isn't really all that relevant, but she might not have had harsh intentions from the start. But she definitely shouldn't have ignored you afterwards0