Bast gets a brief mention in the opening of Black Panther as the panther goddess who granted power to the first Black Panther, but there's more to the character than just mythology. This is, after all, a world where Thor, the actual Norse God of Thunder, occasionally just hangs out in Manhattan, a city that was almost wiped off the map by his brother Loki, also from mythology. That being the case, it won't surprise you that Bast has occasionally taken a much more active role in the comics.
The biggest thing she's done has been to completely change T'Challa's reason for being the Black Panther. After he abdicated the role of Wakanda's protector in order to make way for Shuri to rule, T'Challa was unsurprisingly unsatisfied with civilian life. In order to get his powers back, he journeyed to the necropolis beneath Wakanda's capital, the Golden City, and confessed his desire to return to his former role to Bast, while also telling her that he wished no harm to come to his sister.
Bast's solution was simple: rather than being the public-facing King of Wakanda, T'Challa would serve as the King of the Dead, defending her realm from those who would do it harm. In the absence of the heart-shaped herb that had given him his original powers, he was instead granted the strength, speed, and knowledge of all those who had been Black Panther before him — which turned out to come in pretty handy when he had to lead an army of zombies to attack Dr. Doom after Doom rebuilt the entire multiverse in his image. Probably won't be seeing that one onscreen anytime soon, but hey, it's nice to dream!