。
She has been a popular actress since long ago.
Literal
She [topic-は] long-ago [since-から] all-along popular actress was.
人気のある modifies 女優 as a relative clause: 'an actress who is popular.' 人気 (にんき) means 'popularity.' 昔からずっと combines a starting point (昔から, 'since the past') with continuous duration (ずっと, 'all along'), emphasizing that her popularity has been unwavering. 女優 (じょゆう) specifically means 'actress' — 女 (woman) + 優 (actor/performer).