Online "dating" is really a misnomer - it's really just online "meeting".
Lots of weird stuff like that happens, you just have to accept it's part of the process. Either her old boyfriend made up with her, or someone she dated last weekend turned out to be a great match, or she's someone who realized she's not really ready to date, or she's some scammer who had no intention of meeting in real life. You may never know - just move on to the next one.
Part of what's weird about the online thing is how you may have several contacts going on simultaneously. Can be good and bad.
