Yo Collie Pom Pom: A Slice of Heaven on Jupiter.

Myra Makamae is a burnt-out Magical Girl with a PR problem. After years of saving a world that mostly hurls hot coffee and insults at her, Myra's career comes to a sudden, violent end during a botched bank robbery. But death isn't the escape she hoped for. Deemed too good for Hell and too "unpleasant" for Heaven, Myra is exiled to a divine rehabilitation colony on the frozen wasteland of Jupiter. There, she is enrolled in Auxiliary Haven Academy, an institution where the afterlife is strictly divided between the pampered "Baron" elite and the "Servant" tier, who are forced to cater to their every whim.
To make matters worse, a bureaucratic mix-up forces Myra to trade her magical frills for a butler's uniform. Disguised as a boy to avoid a nineteen-millennia detention, she must navigate a school filled with eccentric high-society snobs, "Death Courses" designed by the faculty, and her own chain-smoking, talking collie familiar, Dastan.