。
Unlike that man, she seems very happy.
Literal
She [topic-は] that man [from-と] differ [and-て] very happy looks.
~と違って ('unlike X') is the て-form of 違う ('to differ'), used adverbially to set up a contrast. Literally 'differing from that man, she...,' it functions as English's 'unlike that man.' 幸福そうだ uses the visual evidential ~そう attached to the な-adjective stem 幸福 — describing what the speaker infers from looking at her ('she looks happy'), not a claim about her inner state. 幸福 is the more formal, written-feeling word for happiness, contrasting with the colloquial 幸せ.