Home for the Holidays by Jordan Silver

When Samantha’s brother cheats on his wife with her best friend, this no nonsense beautiful nerd as she’s known to her friends and enemies alike don’t buy the story that’s floating around. She’s always known her bro to be a sensible guy with morals, but this dude is nothing like the boy who’d protected her her whole life.
When Sam realizes that it’s the new mistress who’d started the rumors of her ex-sister in law cheating on her husband, which in turn brought about the demise of her brother’s marriage, this computer expert put on her thinking cap and got to work piecing the puzzle together. Once she had the real truth just in time for the holiday and with the pandemic keeping everyone close to home, she thinks this is the perfect time to exact her revenge.