、。
She lives alone, but she never thought of herself as lonely.
Literal
She [topic-は] alone is [but-が], lonely [quotative-とは] think [thing-こと] [topic-は] didn't-exist.
Two interesting wrinkles. 一人だ here works as 'is alone' (a state, not an adverbial) — the copula だ predicates the noun 一人. The clause-final が softens into 'but, however.' The negation pattern ~とは思うことはなかった is layered: と quotes 寂しい ('lonely'), は contrasts that quote against other possibilities, and ~ことはなかった ('there was no instance of') generalizes the negation across all moments — 'never had such a thought.' Stronger than 思わなかった ('didn't think'), which would be a single past denial.