Hi Audrey,
Thanks for reporting back. It's always nice to get an update.
It sounds like you have the exact same problem as me, so I can totally relate. I went to Diver's Direct and tried on six different women's jacket BC's in row - all different brands. I'm not "small" but even the size Smalls did what you are describing, because although I'm 5'5", I'm short-waisted, and I have the small-waist/hippy hips figure too, so.... up she rode until I had the shoulders around my ears. It's hard to defy the waist!
You may be able to work with your current BC if you can convince the cummerbund to ride below your waist with a crotch strap. And maybe you could find a different jacket BC that would fit (I tried on a lot of them, but not every one in existence).
On the other hand, I can say from experience that a backplate and wing setup will be able to fit you just right. The plates come in small, medium, and large (or variations thereupon, depending on the mfgr), so you can get one where the waist can be around your waist, and the shoulders can be in the right place on your shoulders. Also, with the waist strap being so much less "tall," from top to bottom (it's a 2" strap not a ~5" cummerbund) the bottom of the strap can be at your waist without forcing the whole works up so high.
I realize I said all this above, but now that we have heard back from you (and knowing the frustration I went through trying to get a BC to fit), I wanted to reply once more.
I can't say for sure that you won't find a BC to fit, or that you will like a backplate/wing; but I can say that it is very, very likely that you will find a backplate/wing that fits you properly.
B.