。
She got into the car and drove off.
Literal
She [topic-は] that car [target-に] get-on [て] go-end-up.
~に乗る ('get on, board, ride') uses に for the destination of boarding — you ride into the vehicle's space. The te-form chains it to 行く ('go') for 'get in and go,' and ~てしまう adds completion or finality, here suggesting she's gone for good or at least leaving the speaker watching her depart. The flavor depends on tone: a sad farewell, an annoyed observation, or a neutral report of someone's departure.