。
She glanced around the inside of her room.
Literal
She [topic-は] her own room's inside [object-を] in-a-sweep [adverbial-と] looked-around.
ぐるり is a 擬態語 (state mimetic) for a single complete sweep — typically of the eyes or a turn of the body — distinct from ぐるぐる (continuous spinning) or きょろきょろ (restless darting glances). The optional adverbial と locks it into adverbial use. 見回す ('to look around, survey') is itself a compound verb (見る + 回す, 'look + turn around'); ぐるりと reinforces and visualizes the sweeping motion.