hey there... this is going to be tough for you. your first relationship and your first breakup are going to feel white hot in the moment and remain incredibly vivid in your memory for a long time. and thats a good thing, because those emotions are important to feel and remember. and as you get further and further away from all this you'll start to notice red flags that you never saw when you were with her. file those away, they'll be important to look out for when the next person comes along.

but back to what I said about everything feeling really vivid. this was your first relationship and you made a lot of memories with her... did a lot of things... felt a lot of feelings. the intensity of first loves is exactly what eventually causes most of them go down in flames. and it may not seem like that now, but thats a good thing. imagine if you had been with this person for years instead of months... decades, even. imagine if you'd spent that much of your life with her, never experiencing anyone else, only to have her run off and get back with her ex. no, you spent 7 months learning about how to be in a relationship, how to relate intimately to another person, what love feels like, what heartbreak feels like, and now you'll be able to use that knowledge to make your next relationship(s) even better.

take your time getting back out there, and don't feel like you have to jump into another serious relationship with the next compatible girl who comes your way. experience a lot of different people and find out what you like and what you need. you're angry because your ex played you for a fool... and I would never suggest you should feel any other way. but think of it this way: she's clearly a very troubled person who is perfectly willing to lie to those she cares about and make herself miserable. if anything you should pity her because she has to live with herself whereas you dodged a fucking bullet. you can walk away with a clean conscience.

lick your wounds for a bit, but don't sweat it too much. she did you a huge favor by showing you who she really is, go find someone who deserves you :)