When did Willows apperice first start to change when useing magic?

[tec]

I got this bit of stage direction from Bargaining Pt 2 shooting script
ON WILLOW - Eyes black, hand outstretched.
This is from the fight with Razor

My question is this when did it first start happening? did anyone notice? what was said?

 

[EVIL UU]

In "Becoming: Part 2", when she's cursing Angelus.