During the quest https://en.uesp.net/wiki/Tamriel_Rebuilt:Andothren_Charity, when you enter the Andas Estate with Ravur Othravel following you, she enters the interior with you, but stops being a follower, which is most likely intentional.

After you're done with Tholer Andas and ask Ravur to follow you again, she instead disappears and you can find her in the Andothren temple, where you can pick her up as a follower again.

According to the UESP, she is supposed to automatically return to the temple when you enter the Andas Estate, which would make sense.