Anyone else find it really strange that they plan an episode for Pinkie to have a sister show up, but they create a new one out of thin air?

Considering she already had two established sisters from the cutie mark flashback, and it's not like they have any personality established so far, it's weird they just wouldn't use one of them as Maud's colors. It'd still be the Maud we know, just look different to match up.

Just kinda baffles me a bit, as I see no reason why they'd do it this way. Unless they have something else for them later down the line, which I kind of doubt.