Folks that are mad at Bee, do you forget what it's like to be angry, despairing, or some other intense emotional state? The words just flow out sometimes... She's not actually angry at Will, but that anger probably stems from the fear of losing Menel and others (e.g. if Will gets himself in trouble again) that she's become close to.
In fact, as others have mentioned earlier, Will needed to realize the reality sooner, otherwise he risks putting the entire operation at risk if he can't manage to understand the actual strength of his forces, as more situations like the Chimera could come up again.
Bee also doesn't know Will's backstory... so when someone more powerful for you has a scary look, wouldn't you be anxious too?