It's rude to tease someone about their hair.
Jenna's sister was trying to save money for a new car, so she went to a hair salon and got a disastrous haircut.
Jenna wants to avoid lying about her opinion of the haircut.
Jenna tells her sister that she has some beautiful head scarves she can borrow.
Jenna tells her sister that her hair's so short she looks ready to enlist in the military.
Jenna's sister thanks her and says she wants to sue the incompetent hairdresser.
Jenna's sister responds that Jenna's hair looks like a rat's nest.