Hermione doesn't swear in the muggle world.

(She does, actually, but never with muggle swearwords and never in public)

Eleven-year-old Hermione- muggle Hermione, in other words- did not swear and did not want to.

Eighteen-year-old Hermione- torn Hermione, in other words- does. She still does not want to.

Sometimes, when she's with her parents-
she feels eleven.

Keep your elbows off the table, don't forget to return your book, Hermione, it's time for tea, why don't you call one of your classmates, it's a nice day out, did you brush your teeth, dear?

Eleven wasn't a good age, she decides.

(Watch your language, Hermione. Yes, mum, sorry.)