SHE MAY GROW SLOW,
SHE HAS STATS THAT AREN'T HIGH
BUT THIS GIRL'S
ONE HELL OF A GUY

So I did some research, and the results are a bit unexpected, but they're not as horrible as this post would have you think. As one post put it, "Fast and accurate, but her HP and Strength are oddly low."
She's also got a great defense growth rate, apparently 65%. That's actually a pretty unique combo if you ask me, but I can see why it might be a little difficult to work with. Of course, she can always reclass to ninja, where a defense and speed combo sounds pretty deadly, and while I'm not sure about her promotions, they might be more rewarding. Not to mention, there's always stat boosting items to help her slow growth rates.

tl;dr Rinkah's still got potential, if you ask me.