Cupid's Revenge by Wibke Brueggemann

For fans of Casey McQuiston and Alice Oseman, a girl falls for her best friend's crush in Cupid's Revenge, a queer young adult rom-com from Wibke Brueggemann that's equal parts hilarious and swoon-worthy.

It was never Tilly's intention to fall in love, but Cupid will get you when you least expect it. That's exactly what happens when Tilly's best friend, Teddy, ropes Tilly into a plan to woo his dream girl, aspiring actress Katherine Cooper-Bunting. It turns out Teddy's not the only one who finds her dreamy.
But Katherine is off-limits. The only thing more important than Tilly's feelings for someone she just met is not hurting Teddy, whose heart has been broken in the past.
Avoiding temptation is easier said than done, as Teddy convinces Tilly to help him audition for a local play as a way to get to know Katherine better--a complete horror for someone who grew up in an artsy family but doesn't have a creative bone in her body. On top of dealing with her growing feelings for the girl she shouldn't like (but who may like her back), Tillie is still grieving a loss while navigating her grandfather's recent Alzheimer's diagnosis. So yeah, that's a lot for any sixteen-year-old to handle without Cupid's vengeful arrows getting involved. Hardcover; 400 pages