My son wanted to marry me and live at home for ever, that's what he used to say when he was 5ish. Now he understands better that when you grow up you leave home and have your own family. He asked why i wasn't married too and I explain i haven't found the right man yet, but that I hope I will one day.
I also distinctly remember saying i'd never have babies when i was a child, because it was far too icky and painful to actually have one. Things change when you are older though.
I wouldn't worry too much about it, but would say don't ignore it when she talks like this. If you can use examples around you of good male role models, even if it's in stories or sopa operas or whatever. And if you're hoping to find Mr Right still then talking about it might help her see that having someone to share life with can be important, but isn't the be all and end all and it's more important to find the right someone than just any old someone perhaps.
Gilly