My graduate student helped with the research that led to my invention. Is she an inventor, too?

It depends. Did she contribute to the conception of the idea and reduction to practice of the invention? If so, she is an inventor. However, if she acted as an assistant, followed your instructions, and performed the necessary labor under your tutelage, then she probably isn’t an inventor. Inventorship is a question of law and is best determined by an experienced patent attorney when there is a question.