How to ask girl if she led me on?

So sorry your heart is hurting. Not fun. The best thing you can do at this point, however, is - as you said - move on. I'm thinking it's best to not ask her if she lead you on. This will only make you sound desperate. But, if you actually do move on, or appear to - and you don't call her or pin her down with questions about why she broke your heart, there is a possibility she may reconsider. As a woman, I can tell you there's nothing less attractive than a groveling guy. Let her see your strength and that you're worth more than letting her walk on you. And, by the way, as trite as it might sound - there really is life after this. You'll meet someone who deserves you and it will be like night and day.