Fiona has a lot of disdain for Frank. That is evident in this Shameless scene.
Fiona ends up lying about an incident involving road rage on Shameless. "My Oldest Daughter" is the second episode of the show's fourth season.

Shameless Season 4 Episode 2 Quotes

Carl: Ew cankles.
Frank: Like a teenage lacrosse player on the rag retaining water.

You'll have to excuse him. Puberty has turned him into a barbarian.

Fiona [about Carl]