BEA Arthur had a mouth on her. At yesterday’s “Celebrating Bea Arthur,” Rue McClanahan told a touching story of how her sister “Golden Girl” comforted her after her mother died. But then McClanahan recalled how her husband came up to Arthur one night at Sardi’s, where the star was drinking alone. He introduced himself as McClanahan’s husband, to which Arthur replied, “Rue, I love. Betty White’s a c – – t!” Angela Lansbury, Rosie O’Donnell, Norman Lear, Adrienne Barbeau, Jerry Stiller and others contributed less ribald remembrances of the beloved star, who died this spring.