I agree. It's a binding issue unless she gets a tune and that fixes things.
@SquidWeaselYay I am going through this EXACT issue and am sorting things out. Only difference is I have new boots vs. new skis. However, same outcome: My beloved Nelas are perplexing me and I have about 50 days on them this season and have been loving them. Got into the new boots, which feel lightyears better laterally without the toe shims and with some minor canting changes, however, I suddenly feel like I can't get to the front of the Nelas. Yet I can edge them like I've never been able to. It's a fore/aft issue as is yours, I think. And a different binding delta can definitely mess with the fore/aft. Even more perplexing is that I was so balanced on my Santa Anas yesterday after struggling in them earlier this season. Same binding, different mount point. I am going to shim the toes temporarily tomorrow to see if I just need the binding shimmed on that ski (the Nela.) The Nelas do have what my husband refers to as a more "traditional" mount point (further back) which with small footed gals like us, can really change how a ski feels and performs. I'd much rather have to shim the binding than redrill and remount it (which is a crapshoot anyway--if it works, great, but if it doesn't, you have an unnecessary extra set of holes in your skis.)
Even funnier is that I demoed the Santa Anas last winter at Big Sky and loved them. They had Squire demos on them, so I bought a pair with regular Squires. Liked them, but man did my quads hurt. Got them home in powder, and I could NOT stay centered. So even the demo binding vs. non-demo screwed me up. I finally threw a pair of Wardens on them which with the new boots had me smiling big time yesterday! Even on the groomers, which I usually don't like on my 98s.
It seems the are so many variables, especially for those of us with small feet, that can throw our balance. That being said, sometimes it does take some adaptation to a new ski to figure it out. It shouldn't be THAT hard, though. You can only shift your weight so much before it's just a massive chore.
I'm taking the boots to my fitter tonight to have the cuff adjusted on one of them. I'll pick his brain. He's pretty adept at alignment issues. Sometimes it just takes experimenting because we're all different.