Why does she make that noise?

The Grump is not a very nice cat. Recently, whenever I ask her to play, she has started to make strange noises. I just walk up to her, and ask politely if she would like to play a game of tag, because I am very bored. But she hunches over like a "gar-goi-ul" (as GoG puts it) and makes "grem-lun" noises like "rrglgrllrgrlrlgrllrggrlrlllrlglrlg" really low. And then she runs away. And I only wanted to play. And I asked really nicely, staying two feet away and addressing her paws and all that. Why doesn't she like me? But Tiria is being nicer. She lets me share the Warm Bed with her. But I have to stay at least a foot away, or she makes a funny noise like "k-k-krrprr" and jumps off. So why does the Grump behave differently?

I'm still the king,
Henry