Hazel's Phantasmagoria - Leander Deeny

Hazel travels to her Aunt's country house for a holiday. Her Aunt is angry and rude, so Hazel expects her stay to be a nightmare - little does she expect, though, that there are actual nightmares living in the garden. These creatures - scary amalgams of different animals such as gorillas and leopards - haunt her Aunt every night. And soon, Hazel is drawn into their world of creating and rehearsing these nightmares . . .
With her new social circle consisting of gorillas crossed with leopards, pythons crossed with porcupines, and wooden-headed dogs, Hazel is thrown into a funny, scary world and learns a useful lesson about friendship along the way.