。
She's the one taking care of us, you see.
Literal
She [exhaustive-が] our care [object-を] is-doing for-us [explanatory-んだ].
Notable for its particle choice: が rather than は marks 彼女, identifying her uniquely as the caregiver — 'it's *she* who takes care of us, not anyone else.' This exhaustive-listing が is what English does with cleft sentences ('it's X who does Y'). The contracted ~てる (instead of ~ている) and the explanatory ~んだ both signal casual spoken register. ~んだ here adds 'as you may not have realized' — explaining or clarifying the situation for the listener.