How to add a new biography (not myself)?

@jeorj_euler​ thank you so much for the information! Could you tell me please, if I sign up for imdbpro, would I be able to do it myself for her there?

If you are her agent, Mary Duker, then claiming her name page would indeed be a suitable course. The prerequisite for doing such a thing is to have an IMDbPro subscription, for which https://help.imdb.com/article/imdbpro/your-account/how-can-i-join-imdbpro/GDBR9HJWYWLEQK7K# provides instructions on how to get started. You may want to register a separate IMDb member account for this purpose, so that you could hand it over to your client without complicating your badges, lists, ratings and contribution history. Once (if ever) the name page itself become unclaimed, it will have to have at least one filmography item on it in order to not be eligible for deletion from IMDb. There is a variant of IMDbPro that is free of charge, so it may not be necessary to maintain the premium variant, the standard IMDbPro. The instructions for claiming a page are at https://help.imdb.com/article/imdbpro/manage-your-imdb-page/claim-your-page/GXWAJBBV8EVPF3PE#, but you may be looking to create a new IMDb name page altogether, which would be necessary if your client's name cannot be found in the search results. The IMDbPro interface itself guides you (as a new subscriber) through all of this.