Unknown credentials for company blog

Hello,

I’m a new marketing specialist hired by a company and I had a question.
A previous employee at our company managed the company blog and had the credentials for login/ access. The “password reset” link is distributed to her (now defunct) email account.

The company CEO has tasked me with trying to get into the blog…which is of course hosted on our company website.

What can I do to get in the site? We don’t have the PW or a means of accessing the reset PW.