My partners adult daughter in her 30s is always trying to come between me an her Dad. We got engaged recently and she would look at my engagement ring

Its like a silent tug of war but she always acts so innocent to her Dad. When I try to explain her actions to my partner I'm met with aggression and acusations that I dont like his daughter. She has done many things in the past that are too many to mention. Her Dad is Italian and worships her. I feel the relationship is doomed as I dont attend family events anymore and she also turned my partners daughter in law against me but ill never find out what she said. Exhausted trying to figure out all this. Im not even sure if my partner genuinely loves me. I think he loves me when alls going well for him. Thoughts🤔 can this survive? His ex wife I think is in it to. So much jealousy!!😩