Betty Ross Syndrome

A girl who knows full well a guy is likely to cheat, hurt her and be an inconsistent loose cannon, yet instists on trying to 'fix' him under a narcissistic and twisted delusion that she's just the special girl out of everyone that's tried to effectively 'Tame the Incredible Hulk'

"She's still with him after he cheated 3 times and everyone around them warned her about him? She must have Betty Ross Syndrome."