Meyer said those words during Eclipse not New Moon books promotion.
Which makes me think that she changed her mind after NM publishing and at that time she tried to explain things which did not happened before. Because there is not ground for existing Bellas love toward Jacob in romantical sense. If we speak about sibblings love, yes. Romantic? no. Bella never felt sparkles at Jacobs presence, more, she never was irritated with Edward which would happened if she would fall in love with another boy.
Let's say that you are right and Meyers didn't write Bella to be in love with Jacob in New Moon at the time that she wrote NM. Then as she was writing Eclipse, there was obviously something more than graditude towards Jacob for helping her in the few months that they were together. So as Meyers is writing Eclipse, she realizes that Bella does love Jacob. So what does Meyers do? She confirms that for us, but because NM has already been published she cannot go back and add more to the story. So Meyers uses the only things she has which is her website AND Eclipse which she is currently writing to explain what she couldn't put in NM because as the author she hadn't thought of it yet. So IF Meyers changed her mind or simply hadn't thought of it yet when writing NM, that does NOT mean that it is not true. As the author, she has every right to do with her characters whatever she wants. IF what she wants is not supported in the text of her story, then that makes her a bad author, but as readers of HER story we have to trust what she says to be true.
In that case she ruined or at least seriously damaged her own world of Twilight.
I do not think that Meyers feels that way.
Her words in regards Bella loving Jacob.
"Does this love devaluate her love for Edward? Not for me. For me, it makes that perfect true love stronger. Bella has another option. She has a really good one. An option that's easier in many ways, that takes nothing—like her family, present or future—away from her. She would have love, and friendship, and family—an enviable human future. But she chooses Edward over all of this. This makes it real for me."
First, marriage with Jacob would take away her lifestyle and personality.
But the main objection is this: her script is impossible. There are no return ticket to love. If Bella falls in love with Jacob, it means, her love toward Edward is gone. IF she still chooses him not Jacob, it would mean she prefers wealth and beauty forever... not love.
". If Bella falls in love with Jacob"
-- I don't think you can say IF because Meyers has made it a fact that Bella did in fact fall in love with Jacob. Those were Meyer's words and not my own and so it seems that she would disagree with your assessment and that Bella still loved Edward and chose him because she loved him MORE not because she didn't love Jacob.
I think Meyer started writing Twilight from what she felt. Her writing came from her heart - in beginning. Later [during Eclipse] she was confused how to expand story and she tried to think with cold mind, and only then she decided that Bella could be attempted by another love interest. But such twist does not work because there is not any logic (1) and Meyer herself never proves Bellas love toward Jacob (2). Her words are not proof because she spoke about it but did not write it. Bella never felt any sparkles at Jacobs presence which she should because this is not coming from knowing, it is thing of chemistry between lovers even they are not aware about their feelings yet. (Compare with first touch of B and E during their first conversation in Twilight!) And she easily left Jacob, always. Actually, Bella never made choice.
But Meyers is the author so her WORDS should trump anything that she wrote. She is explaining with words that she didn't express very well on the page. I agree that Bella's love for Jacob is not very clear except for at the end of Eclipse. I do feel like Bella herself makes it very clear that she IS in love with Jacob. Bella confirms that Jacob had been right the whole time, that she was in love with him. Even Edward confirms it saying that she loves Jacob and she didn't deny it, only saying that she loves Edward MORE she could have said that her love for Jacob wasn't romantic but Bella did not say that. Instead after Bella leaves Jacob and Edward is holding her she wishes that they were Jacob's arms instead of Edward's. This is clearly a girl who is conflicted and as she cries all night even Edward doubts if she is making the right choice. I know that it doesn't feel like Bella really spends much time thinking and debating "Edward or Jacob, Jacob or Edward, Edward or Jacob..." like maybe she should have but I'm kind of glad because Eclipse was long enough without adding that because we all know that Bella loved Edward more than Jacob so no reason to draw out the inevitable (Jacob's broken heart).
My problem with Meyer is, her words contradicts with her writing.
I disagree with her theory about having another love interest as a proof for the real one - for me it says something about unmaturity and having no clue what real love means - but the point is, Bella never feels or shows her romantic interest about Jacob and she never doubts about her choice. Like I said before, no matter if she knows herself or not, she should feel the sparkles in Jacobs presence... but she never does. We can't speak about her choosing Edward or sacrificing love toward Jacob if she never does it. Her hysterical crying is not choice... she whines mostly about her behaviour not about others.
Meyers is showing two very different types of romantic love.
1) A more instant and sweep you off your feet type of love, with sparks and electricity. This attraction really doesn't have to do with the personality but the person.
2) A much more subtle love that develops lowly and has everything to do with the personality of the person.
My personal bias is that I do not believe that the first type described exist outside of fairytales. It is not real. You on the other hand seem to not believe that the 2nd type of love exists. What WE need to accept as the reader is that Meyers DOES believe that both types of love exists and that Bella experienced both types with two different guys. We don't have to like it but we do have to accept it because it is not mine or your story. It is Meyer's story and therefore SHE can do anything she wants with it.
I do believe those both type of love but I do not believe possibility to be in love with two at once.
My biggest problem with Meyer is this: she writes one thing in the books and says opposite thing in interviews.
One more thing. Those words much more subtle love that develops lowly and has everything to do with the personality of the person much better suits with Edward not Jacob. Remember, Bella and Edward spoke very much, they shared words and thoughts, and their dreams. Nothing from that happened between Bella and Jacob. There were some laugh and easy talking, and Bella felt herself good... but she never shared her dreams, thoughts and future plans with Jacob. He never got why she was so eager to bike, hike and try cliffdiving. No doubt he believed that she did it all because of him... and this is the reason why he believed he could and should get Bella back!
So funny that Meyer seems forget what she wrote by herself.