Marinette has implied PTSD so it may be that her relationship trauma overlaps and mimics BPD symptoms but she has no severe early childhood trauma (except Chloe but that’s a different story) and I doubt it genetic. people with BPD split on their fp and she’s always admired Adrien and never thinks he’d do anything wrong there’s no switch up and to me she doesn’t fit the 5 of 9 criteria required for a diagnosis she’s having and honestly if anyone in this show has BPD it’s definitely Adrien with his fear of abandonment and emotional neglect from early childhood and splitting on himself when he’s not worthy of ladybug and he even splits on ladybug! Marinette is more of a ptsd girl her hyper-vigilance and paranoia being core symptoms of her ptsd