While the plot isn't exactly as you describe, it features the following:
* Carol Burnett plays a woman named Doris who is trying to win money in a casino to help save her church.
* Howie Mandel plays her angel, but with a mischievous, almost devilish, streak.
It's a lighthearted comedy, and though it doesn't involve a literal devil, the angel's personality aligns with the theme of your description.