She said: "People do think I look younger than I am because I dress like a teenager.
"As women we're so conditioned to think that beauty and age area very important that you stay kind of youthful in order to be beautiful.
"I don't think it's fair for people to think that women are just vain because they're worried about getting older. It's actually really linked in with a lot of very primitive stuff for women."
Portia recently revealed that she and Ellen don't want to have children of their own.
She previously said: "There comes some pressure in your mid-30s, and you think, Am I going to have kids so I don't miss out on something that other people really seem to love? Or is it that I really genuinely want to do this with my whole heart? I didn't feel that my response was 'yes' to the latter. You have to really want to have kids, and neither of us did. So it's just going to be me and Ellen and no babies - but we're the best of friends and married life is blissful, it really is. I've never been happier than I am right now."
- Bang! Showbiz