I agree that Eydie Gorme was one of the greatest pop singers of all time. Her renditions of such Broadway songs as "Too Close for Comfort", "If He Walked into My Life", "What Did I Have That I Don't Have", and countless others are thrilling to hear. I also believe she was genuinely loved and respected by countless entertainment giants like Steve Allen, Johnny Carson, and Carol Burnett, who showcased her talent on their TV shows.
However, the assessment of Gorme's acting skills by various theatre writers and historians is pretty dismal. William Goldman devotes an entire chapter to Golden Rainbow in The Season. In it he details her inability to deliver basic dramatic and comic dialogue effectively. Instead she occasionally employed phony little tricks and gimmicks to get through certain scenes in order to satisfy an undemanding audience.
I think Stark, Robbins, Styne, and Kanin made the right decision in casting Streisand and Chaplin as Fanny and Nick in Funny Girl. Of course, just IMO.