。
She was dressed like an actress.
Literal
She [topic-は] actress-style [in manner of-に] was-dressing-up.
The suffix ~風 (ふう) means 'in the style of' — 女優風 = 'actress-style.' It attaches productively to many nouns: 和風 (Japanese-style), 洋風 (Western-style), 学生風 (student-looking). 装う (よそおう) means to dress up, adorn oneself, or present a certain appearance. The ~ていた indicates this was her ongoing state at the time being described — she was dressed up in an actress-like fashion.