Because it was the 1930s and the Waltons were Baptists. You can't apply today's sensibilities to a period piece. It would have been a HUGE issue back then.
That and any girl of not the same religious background would have been a huge issue. The show buckled in the religious aspect when Toni showed up but then Esther was a shell of herself and Michael Learned was pretty well off the show. It would have been a major credibility issue if Toni had come along in the early seasons.
I always liked John Boy and Jenny together. First love. I kept hoping she would return and they would get married. The arguments he had with Marcia Wollery were funny though.
I would have liked to see John Boy end up with Jenny. They seemed like they had great chemistry. I loved how she loved all the Waltons and wanted to cook his meals, clean his house, etc., I think she would have been really content as John Boy's wife. It would have been really fun to see that relationship develop more.
I agree they had great chemistry! And she fit right in with all the other Waltons. It would have been sweet if they had built their house right there on Waltons Mountain.
From your list I would say.... Daisy Garner. But there were a couple women that were not there, like... Sis Bradford -"The Beguiled", and Madeline Bennett -"The Woman" .
Was Daisy the dancer who gave up her baby for adoption? I vote for her. Her scenes with the Walton girls were genuine. Yes, she had a "past," but I think it would have made for some interesting storylines. Unfortunately that child they cast as her daughter was just so bizarre looking.