I agree with Nai - take it up with HR and let them look into it especially if you think it might be a gender discrimination issue. I would worry that maybe there are issues at play here that you can't see - like budget cuts and other things. If she was only a temp, there might not have been money to renew her contract or the job description may have changed.

Sorry Starfish - posted at the same time as you. I can understand your concerns about gender discrimination and most workplaces take it very seriously. Have a chat to HR because they might be able to look into ways that they can become a more inclusive work environment.