Chell knew she couldn't control him forever, as much as she would like to. That was the reason why she hoped to take him to Engineering, give him some independence and hope he could handle it without going insane. Again. A risk she'd have to take--if they were really in the middle of an interdimensional war, toting him about ad infinitim would be completely impractical and probably get them both killed eventually. And she liked being alive. She liked it a lot.

It also occurred to her that getting him limbs would not necessarily be enough in a combat situation, so weapons were going to be part of the equation, whether she liked it or not (she didn't).

Mashy spike plates, however, were just too soon. Here he was, asking if he could get his figurative hands on the very things with which he'd tried to murder her. For all she knew, he'd just turn around and try to kill her again the instant they were in his possession. So where Wheatley was practically giddy, Chell was positively furious, and certainly looked it, too.