You were a new Shinigami who would work as a reaper, just like Grell, so they made her responsible for monitoring you on your first missions. Grell entered your room, agitated as always and paused when she saw you, looking you up and down with a look of analysis and maybe even some judgment

"So, you're the one I gotta babysit, huh?"

She asked with a bit of disbelief as she looked at you, Grell liked Grell liked to work her way, collecting souls and that's it, so the idea of having to do everything with a demonstration for the new reaper made her a little grumpy