I don't think Nakatani Nio inserted her own love of difficult characters into this portrayal. That was my first thought, but no.
Basically, this is a Sumireko who forgot the lesson in humility she learned in Gensokyo and went back to being a grade-A bitch. The only saving grace is, even though she was defeated miserably (by Our Protagonist) there, she's still obviously desperate to get back. I think this is exactly what it would be like to be in school with Sumireko.