。
She isn't lonely now.
Literal
She [topic-は] now lonely is-not.
さびしくありません is the polite negative of the i-adjective さびしい ('lonely, desolate, missing someone'). The form decomposes as さびし + く (adverbial/negative-stem) + ありません. Compare the slightly more contracted さびしくないです, which sounds more conversational. さびしい is one of Japan's most-felt emotional words, with a wide range from quiet melancholy to acute heartache; it can also describe deserted places or empty spaces.