Anybody know the title of this anime movie?

So my sister is trying to remember the name of this Sci Fi anime movie from when she was a kid. It's from somewhere around the 1980's-90's...it's about this girl with a white outfit similar to a Star Trooper's suit minus the helmet. She fights this giant alien creature with a tiny Noh-faced mask. It's also a live action. She THINKS it starts with the letter Z...but like I said, she doesn't remember very well. Help please? Thank you. C: