Sounds like it's time to start experimenting, AmyPJ ...and drag your instructor and/or boot fitter along with ya if ya can ...but if you cannot, do it anyway...
Pretty easy to put a couple pieces of shim material under the inside edge of your left boot as an experiment to test if additional canting will help. Experiment inside the boot as well building up support on the inside edge - get out the tape and cut some cereal boxes up ...or whatever...
How is your fore/aft alignment? Yeah, I know you're talking left/right
Experiment with adding shims under your toes and heels to see if anything changes. Also, different binding/ski combinations will change this - potentially a lot; and with greater effect if your BSL is short.
How's the balance on a flat surface standing on the left foot? How about while standing on your footbed? What's different when you are in your boot on the flat surface? What's different when you are in your binding on the ski?