I really don't see him selling out Boogie, for example. I think he knows he needs a stronger player to align with to get him further in the game, and Janelle has proven herself to be one of the strongest in the house.
While Will may eventually "throw Janelle under a bus" (term for BB7 apparently!), I think if he feels he can trust Janelle, he would target the other Sovs if given a position of power (doubtful, but Boogie may eventually, and they share a brain). And if two Sovs were nominated by a floater at some point, rallying her other two sovs AND CT (and Marcy) could keep her in the game.
I think she really does see Diane as a threat. She is much more capable of winning endurance competitions than either Boogie or Will AND if one of Chilltown was out of this game, she is sure the other person going up in a Diane HOH situation would be her.
Sure, by nominating Diane instead of Will, you are playing into his game and he is one step closer to doing what he did his season! Which would be hilarious!
And from a viewers point of view... Will is much more entertaining than Diane