Like I've mentioned before, Dusk and Twila both have control over this form. When one is in control of the head, the other tends to take control of the body. 

One thing I haven't mentioned is that the two actually share all of their senses now too. If Dusk eats something, Twila will actually be able to taste it. And if Twila grabs something or lets something touch her body, Dusk will feel it. 

With that in mind, the first few months of the two sharing a body are...strange. They can somewhat sabotage each other if they're feeling particularly spiteful. Twila is a lot better at doing to Dusk than the other way around though since she tends to control the body a lot as Dusk always attempts to go for the head if he can.

One of her favorite ways of spiting him is to act as feminine as possible, exaggerating her movements, doing cute poses all the time, flaunting and flirting with cute guys, etc. Dusk either has to act along or just blush in embarrassment as he can't really do anything to stop her. 

Occasionally, as Twila can be unashamedly lewd at times, she'll get rather horny. And when she does, she'll try to relieve herself in the privacy of their room. Dusk both hates and likes it, since as a guy, he understands and even admits that Twila has a really nice body, and watching it preform lewd acts is admittedly exciting. The part he dislikes is that he feels everything that Twila does. If for some reason, he and her got into an argument (it's very likely and common), it's kind of hard to spite her and stay mad at her when he's feeling immense pleasure. 

Twila knows this and tends to also take advantage of it.