It's hard to tell who is who in this poster, but my guess is that the woman on the left is Ursula, the woman on the right is Gudrun, the man standing is Gerald, and the man kneeling is Rupert. Gudrun seems to be the tougher of the two sisters. She would be the one to slap Ursula out of it, if the situation called for it. Lawrence describes the sister in the following quotation, "Her look of confidence and diffidence contrasted with Ursula's sensitive expectancy" (8). This quotation exemplifies how Gudrun fits the facial expression of the woman on the right in contrast to the woman on the left who would seem to have the facial expression of Ursula. Lawrence portrays Gerald as an ideal man so I couldn't see how Gerald could be the man being manipulated (although, Lawrence didn't make this movie and character portrayal could have been construed).