Martha Vickers

Martha was a member of the cult of the Cailleach under Leonard de Vries in 1978.

Biography
Martha was unwilling to sacrifice the Fourth Doctor to the goddess, and after he escaped, an Ogri killed her and de Vries. (TV: The Stones of Blood)

According to one source, Martha was a local schoolteacher and had joined the cult due her friendship with de Vries and because the cult brought colour into her dull life. (PROSE: Doctor Who and the Stones of Blood)