Gwendolyn was heartbroken! To the point where she became pissed.
Ever since Maxwell was maltreated by the Emporium Academy, she has been unhappy. Then Tammy broke her promise, which made her even more unhappy. Maxwell being crushed by Godfrey's power made her unhappier, and Lucas's sinister and despicable means finally broke the straw.
To her, there were too many things today that made her unhappy. That's why she became enraged.
But it wasn't obvious when she was enraged since her expression didn't undergo that much of a change.
This was only the second time in her entire life that she became enraged!
The first time was when some people in her family set up a marriage engagement against her will. This made her extremely unhappy, so she drew a line between them and intended to ignore them for the rest of her life.
Today was the second time. Her rage was because of Maxwell.
