。
She's not in the kitchen or the living room.
Literal
She [topic-は] kitchen [in-に][also-も] living-room [in-に][also-も] does-not-exist.
Stacked にも...にも...ない is the 'not in X, not in Y' construction — both locations are excluded from where she is. The pattern [location]+にも+[location]+にも+ない exhaustively negates a list of places. いる is for animate beings ('exist, be present'), as opposed to ある for inanimates. 居間 is the standard term for a Western-style 'living room'; the more traditional 茶の間 ('tea room') or 座敷 cover similar ground in older Japanese homes.