Cher might be adding “grandma” to her legendary résumé -- and if this long-buried family secret is true, it came with a plot twist straight out of a soap opera. Former model Kayti Edwards is claiming she dropped a bombshell on the pop icon last year … telling her she shares a daughter with Cher’s son, Elijah Blue Allman -- a kid Cher allegedly didn’t even know existed for more than a decade. According to Edwards, who spoke to The Sun , she and Elijah had a brief relationship back in 2010 that