The show is clearly meant to be comedic both in general, and with regards to the references in particular. Furthermore, the show is clearly fictional, and Tahani is presented as such an unreliable narrator that it isn't clear whether her claims are true even within the show (although some of her claims have been shown to be true within the show's universe). Given these facts, it would be extremely difficult to make a defamation case; defamation requires that the claim be presented in a manner that a reasonable person would take as a claim of fact. See

https://youtu.be/UN8bJb8biZU?t=1207

There wouldn't be much of an intellectual property case to be made, either. They aren't showing actual clips of the shows, so no copyright issues. It would be difficult to interpret the mentions as being endorsement of The Good Place, so no trademark infringement.