Need advice.

So my boyfriend is still friends with his ex girlfriend I don’t have any problem with that, his ex lives in America and we live in the uk they have been broken up for a long time but he’s still friends with her that is not what I have the issue with, his ex has split personality disorder and she stoped taking her medication i don’t have a problem with that if he chooses to support her that is his choice, but what I have a problem with is her other personality still has feelings for him and is completely obsessed with him and has it in her head that my boyfriend has feelings for her,I have a problem with the fact her other personality is going out of her way to brake up are relationship I don’t know if I’m just over reacting or what, what do you think?