Oh sure, she likes you as a nice guy, but she's not into you the way you had hoped.  You go out with a girl, say for lunch or a coffee (something light and easy).  You hang out for an hour or so, eat your lunch, drink your drink...it's a pleasant time.  You pick up the tab (because it's the right thing to do) give each other a hug and you go your separate ways.  You send her an email telling her you had a good time and that you should do it again.  She responds, 'Yes, Let's'  and then...nothing happens.  2 weeks go by and nobody makes an attempt to contact the other.  Safe to say you've now missed your window of opportunity and it's time to move on.

Yeah she can play the 'but you didn't email me either' game, but that's bullshit.  If she liked you (in that way) she would have gone ahead emailed you, facebooked you or whatever.  At least emailed you a bit more than, 'yes, let's.' Maybe she's busy..?  You come up with different justifications as to why she never emailed you back or took you up on the 2nd lunch offer, but bottom line is, she doesn't want to get naked with you.  Which, as long as you don't phuck it up by making an ass out of yourself, is a pretty fast and painless way to let you down.  So let's just hope you're pretty quick at picking up signals. 

In this day and age, especially with email, girls can now be proactive and follow up on a guy they like if they so choose.  Yes, you could have sent out another email, then another but it's best to wait and see if she comes sniffing around first because that will help you plan your next move.  And in this case, your next move is no move at all.