。
Unlike that man, she seemed very happy.
Literal
She [topic-は] that man [from-と] differ [and-て] very happy looked.
The past-tense visual evidential ~そうだった ('seemed [adj]') describes a past impression based on appearance. Note 幸せ here, the everyday colloquial reading of 'happy,' rather than the more formal 幸福. The ~と違って construction sets up the comparison adverbially: 'differing from that man, she...' Putting it all in past tense suggests the speaker is recalling how she looked at some previous moment.