noun / verb
tattle
TAT-ul/ˈtætl/
A childish report of someone's minor wrongdoing.
A girl tattles on a classmate for scribbling on his desk.

Etymology
Tattle probably comes from Middle Flemish tatelen, “to stutter.” Its early meaning of childish prattling developed into talking unreservedly and spilling secrets, providing the bridge to reporting someone’s minor wrongdoing.
In context
you Morgan's little sister used to twist the truth and tattle on her she made all the relatives so biased against Morgan
More examples
- Please don't tattle on your sister for taking an extra cookie.
- His latest tattle concerns a classmate chewing gum.
- She is always tattling about who talks during quiet time.
Forms
tattle · tattles · tattled · tattling
tattletale noun — Someone who childishly reports minor wrongdoing.