、。
When she saw he had dressed up his very best, she chuckled.
Literal
She [topic-は] [he [subject-が] [doing one's best-精一杯's] dressing-up [object-を] did-and-came [nominalizer-の]] [object-を] saw-and, [chuckle-ウフッ] [adverbial-と] laughed.
A multi-layered sentence. The embedded clause 彼が精一杯のおめかしをしてきた describes him having dressed up his best, with してきた combining the action with the directional ~てくる ('came having done'). The whole event is nominalized via の and then perceived (見て). ウフッと笑った uses ウフッ, a sound mimetic for a soft chuckle, set off adverbially with と.