That was over 29 years ago in 1992.
Today she is 71, and has starred in 94 movies in total, 75 since Alien³ was released.
In Alien³, I think Sigourney Weaver looks:
Alien³ scores 6.2 out of 10 on The Movie Database.
Sigourney Weaver's first acting role was as 'Alvy's Date Outside Theatre' in Annie Hall, released in 1977 when she was 27.