Read it a couple of years ago, only remember the major plot points.

Female lead is an angel, male lead is a demon. They'd known each other for a very long time and had this witty banter going on because they were enemies but also kind of friends. He was given an assignment which will basically ruin her career but will free him from his contract or something like that. At the end they have sex (possibly on a beach?), which is a no-no for angels so she's expecting to be punished. He fails his mission on purpose to benefit her, but in the end was forgiven/promoted? by the angels for doing a good deed. I think this was a novella.

Really similar to Ecstasy Unveiled by Larissa Ione, but it was a stand-alone and the male lead was an actual demon doing demon things. The female lead could have been a guardian angel type, but I might be confusing it with Ecstasy Unveiled.

Sorry I can't provide a whole lot of solid details, but any help finding this book would be appreciated