Umbridge finds her sketching, next. And, rightfully, didn't believe she had been given special dispensation to be out after hours.
Detentions were assigned, and when the only information she could offer included Dumbledore's favorite sweets, she was quickly set to write lines.
She hadn't had a plan to handle the quill, but she'd also refused to fuel the woman's sadism.
So, she'd bluffed.
"...interesting invention. I wonder if Rita would consider a promotional piece?"
"..."
"Or, parhaps, Lockhart? I was his favorite student, you know? We still keep in touch."
"..."
"Or, maybe-"
"-you're dismissed."