My friend is looking for light-hearted books (preferably in a completed series)

I have been trying to recommend her some books but her tolerance for 'stress' is quite low.

The Ascendance of a bookworm light novels were almost too much for her, for a general idea of her tolerances (I have not read those novels myself, only some of the manga, and it seemed fairly light-hearted to me, but the light novels go on far past what I've read.)

I suggested Dragons of Autumn Twilight since she plays D&D but the it was too dark for her. She also didn't like The Colour of Magic because she said the humor was too weird for her.

I myself tend to mostly read manga (she doesn't like comic books, eastern or western) so I can mostly only really recommend light novels.

Her favorite books are the Reincarnated as a Slime light novels, I've also suggested the 300 years killing slimes novels to her, but she would prefer a completed series to an ongoing one.

I asked her what she is looking for in a book series and she says she wants 'something with minimal stress'. I asked her to define 'stress' and she said 'sad moments and any references to unwanted sex'.