。
She doesn't mind in the slightest.
Literal
She [topic-は] [not-in-the-slightest-ちっとも] [is-not-minding-気にしていない].
ちっとも is a slightly more colloquial sibling to 少しも — both pair with negative predicates to mean 'not at all, not in the slightest.' ちっとも has a touch more emotional flavor and a faintly old-fashioned ring; 少しも is more neutral. 気にする ('mind, worry about') in its negative ~ていない describes a sustained state of not-minding. The contracted ~てない ending (from ~ていない) is the casual default in conversation, with the い regularly elided in everyday speech.