certainly, i was young when i met her too (17years) but mine was an online longdistance relationship ordeal - 4 years together , 3-4 years apart now.. sounds super similar to what you have said

i had(have) deep feelings for her, and i was convinced she had deep feelings for me.. she told me that she was in therapy and told me her dx was psychopath and i guess when you're in that position you just dont get hit with the full understanding until alot of bad stuff has already happened? she made me feel like i was going crazy as well.. i became paranoid and very jealous to the point where i didnt believe anything she was saying most the time (which was because she was lieing but anyway) and doubted myself all the time even.
to me it has been a crippling experience and one that i dont know how to recover from really, it messed my head up i think... i still send her emails from time to time because i tried to end it on good terms.. happy holidays, bday - things like that... (she responds sometimes, but its always short and i dont know what to make of it anymore.. feel like a fool) its just hard to believe that she could really be that inconsiderate though, but i guess i just made her out to be perfect because of my own problems :/ im not sure what more to add to that ... i dont really talk about it much, but im sorry that you experienced something similar..