The motives of the actress are quite transparent.
The Vampire Diaries is considered one of The CW’s most popular projects, and fans are still focused on the cast of the series, which ended back in 2017. As a result, the supernatural drama became the longest-running vampire show, overtaking True Blood (2008-2014) and Buffy the Vampire Slayer (1997-2003). But, despite the cult status of the show, it was never possible to lure Sarah Michelle Gellar into it.
In the eighth episode of the second season, viewers met with Rose-Marie, who turned Katerina Petrova (Nina Dobrev) into a vampire. The role went to Lauren Cohen (“The Walking Dead”), but one of the creators of the show, Kevin Williamson, dreamed that Rose was played by Gellar. In an interview, he said:
“Initially, my unrealizable fantasies made me try to get Michelle Gellar to replace Rose Sarah. She was grateful but refused.”
Showrunner did not go into detail about the reasons why the actress refused his offer. However, it can be argued with a fair amount of certainty that she was simply not interested in getting involved with the vampire theme again, even if this time she would have to try on the fangs herself, and not kill the undead.
By the way, when the seventh and final season of Buffy ended, Gellar openly stated that she was happy to part with her heroine. In addition, her appearance in The Vampire Diaries would surely have attracted the attention of fans, but left an imprint on Buffy’s legacy as a kind of feminist icon, because after all, Rose did not advocate for girls power at all.