I totally agree with that. .. she was like all over the place, unstable, erratic. I think she's a good actress but I wouldn't count this as one of her better performances. Also, I found that scene out of place in 1940s America given its portrayal of sexuality. Not that I think something like that couldn't happen, but I find it unlikely that it would happen today and less likely that it would happen then.
Maybe she was mentally ill. Or distraught. Jake was just taking a firm hand. The whole movie was off the wall and unbelievable like the court room scene and portrayal of lawyers and police in general. I could not believe the scene when Jake pulled a gun on Loach and stuck it in his mouth at the police station. I think someone would have hit him with a black jack or at least pulled a gun on him. The scene from Basic Instinct when Nick attacks Nilsson of IA ends with a gun up against his cheek and two other cops restraining him. Jake would be unconscious or dead for assaulting a cop with a gun in a police station.