Internet Archive's wayback machine? Your tech advisors may be able to copy the HTML (source) code by right clicking on the archived page, and then use that code to recreate the essential page elements.
If she was an employee ... If the executive director was an employee of the nonprofit, and if the website was created within the course of her employment, then the nonprofit owns all the content including the appearance and design. That's a basic principle of copyright known as an employee work made for hire. However, having an official title of executive director and managing the checking account don't necessarily make her an employee. Use the government standards for judging whether she can be categorized as an employee or contractor.
If she wasn't an employee ... The nonprofit might still own all rights to the website if there is a contract or other paperwork setting out the executive director's obligations and transferring ownership to the nonprofit. Also check the nonprofit's bylaws in the event they address the ownership issue. Even if there is no paperwork and you conclude the director was an independent contractor, not an employee, there's a good chance that the nonprofit acquired a nonexclusive implied license to use the materials provided by the executive director. Finally, it's possible that the elements contributed by the director are not copyrightable by her -- perhaps because they are based on other material or because they lack sufficient originality to qualify for copyright protection.