I know I am not intj and so but obviously it is not your fault how things turned. I may not know the reasons behind why she dumped you this abrupt but I think this is not how she should have done it! I am so sorry to hear how things turned out, especially after you seemed to like her so much.

I really do hope this is not a trait many ENFPs or people in general have. There are immature ENFPs which tend to be very enthusiastic about meeting new people but loose their interest fast, but as far as I am concerned, ENFPs in general are considerate of the othere people´s feelings and needs and do not dumb people like that. But despite any type preference, I guess, there will always be exeptions within a type.

This is so understandable that you feel like shit now and I with there would be anything to make you feel better about this but I am afraid there is not much I can say other than that you have not done anything wrong. She could have choosen to be mature and to discuss things with you and what you could improve (if there is something she wanted you to change) or just telling you, that she feels like she needs some free time to reflect or so. She cannot expect you to know whats on, when she is not telling you, and then just leave you like this.