teatime-with-maddie answered:
Sparrow and Duchess both have very few friends. Up until True Hearts Day, they basically seemed to be the only friend the other had. They were always together and that made people ship them. Yes, in True Hearts Day Sparrow cut ties with Duchess, but just because he didn’t want to be her lackey anymore, doesn’t mean he would be unwilling to be her friend in the future.
They were clearly together in the background in Spring Unsprung, so they are at least speaking again. Flirting with other people doesn’t mean you can’t be interested in someone else at the same time. Daring flirts with everyone. That doesn’t make ships with him as one of the members invalid. So why would flirting make ships with Sparrow or Duchess invalid?
Entire ships are build on characters standing near each other and looking cute together. Duchess and Sparrow shippers have a lot more than that to go on. Mattel even implied that they might be involved in a romantic relationship. Obviously that didn’t happen, but that doesn’t mean it can’t happen in the future. I think they work well together and would be good for one another.