you explained everything perfectly when you said she beat herself to you and then pulled away.
young females will do that and walk away in the blink of an eye as if nothing ever happened.
you got your feelings wrapped up in someone who wasn't serious in the beginning and just needed someone to take her mind off her ex.
it's no coincidence that you and her ex had the same name. all along she knew exactly what she was doing.
As a young immature person to love you fell for it and you have just experienced your first true heartbreak.
people always say your first love is your worst love,
ultimately you'll find someone who deserving of your love just keep that good pure heart and make sure when you do love again you love someone who's capable of whole-heartedly loving you back.
she couldn't do that because from the beginning she was not open to loving again and she didn't even know it herself
forgive her and move on with your life