Its not fair that shes using you. Does she not make love to you at all? If not she is 100 percent using you. I am a female witj bpd and used to only go for older men and i got used and treated badly but i couldnt let go. I did the same kind of klingy and dramatic texts. If their older than you they can mannage to win arguments, turn things around and get their own way.
Is there any reason why you wouldnt consider dating a girl nearer your age? I wish you the best of luck