。
She had the hotel suite all to herself.
Literal
She [topic-は] hotel's suite-room [object-を] sole-monopoly did.
独り占め (literally 'alone-occupy') means 'monopolize, have all to oneself' — taking up something exclusively. The light-verb construction 独り占めにする adds the adverbializing に before する, giving 'do (it) into a state of sole occupancy.' スイートルーム is a katakana loanword from 'suite room' — note the Japanese 'suite' uses the spelling distinct from スイート ('sweet'). The hotel suite as image is itself a Western luxury concept transplanted into Japan via the foreign tourism boom of the 20th century.