Although I have no experience in a relationship such as this, I have been emotionally and verbally abused by a parental figure. Being manipulated is not cool. If you are feeling it, it is happening. My (inexperienced) advice would be to talk to your direct partner and let them know the situation, and how it makes you feel. If they love you, they will want the best for you, but they may not believe you about their loved one (they may be in denial). You need to be prepared to leave if your partner can't understand. You can't bow down to emotional bullies, it ruins your spirit. Seriously.
Abuse is abuse, sometimes it is worse when they leave no marks, like in your situation. It can't be proven but it is just as damaging. Take care of yourself, first and foremost. If you need any support, please feel free to message me!