The Last Angel — Jon Jacks

Everyone has a guardian angel: an angel who regularly offers you sound advice, and soothes you when you're angry.
Chrissy's angel Jial, however, is more like a little sister to her.
She's lots of fun to have hanging around, to watch movies with: but she's also way too lenient.
Chrissy loves her.
And when the angels start inexplicably disappearing, it's Chrissy's turn to guard her angel.