She's tense, every muscle trying to prepare itself for what she's going to need to do. Her thoughts are on that and that alone, so even if Chrono wasn't moving faster than she can see, it would have taken her a few seconds to comprehend precisely what had just happened.

As it is, she watches with a blank face as Collette falls down into the room for a few seconds before she really understands, and then she's already starting to move, though she fixes Chrono with a look as she does so.

It's a look that asks: really?