I think there's a difference between knowing it could hypothetically happen, and having it actually happen and acting like the status is still quo.
She knew he could potentially still be evil if he wanted to, but up until the deal with Adam, he showed no real inclination for it. But then he sold them all out to a demon who wanted to kill everyone. She knew he could try to get the chip out, but up until OOMM, he hadn't. But then he did, and immediately tried to kill her. I would expect both of those things to create more distrust of Spike than it does.
no subject
She knew he could potentially still be evil if he wanted to, but up until the deal with Adam, he showed no real inclination for it. But then he sold them all out to a demon who wanted to kill everyone. She knew he could try to get the chip out, but up until OOMM, he hadn't. But then he did, and immediately tried to kill her. I would expect both of those things to create more distrust of Spike than it does.