I'm sorry, I'm still smiling
... That's a good
question - and I hope someone else has a good
answer - but in case they don't, I'll take a stab. -Thinking out loud- I done the opposite a few years ago; I had an apple on a 'semi-dwarf' rootstock struggling in orange clay, so I purposely mounded soil up and over the graft union so that it might 'root' - and go 'wild!' No signs of wildness
If you dig soil away, you'll create a sink up against the trunk, but if you leave it, the fruiting variety will / may root, and loose the dwarfing affect. Do you need it dwarfed? (from personal experience) If you prune an apple tree yearly, they can be kept to about any size you desire. I'm no longer scared of a 'standard tree' - I just whip out my Felco Eight's!
If you definitely need / want the dwarfing, and you feel it's worth disturbing the tree ... I'd reset it ASAP!
I don't know how vigorous Pink Lady is? I've a limb of Pink Pearl, and it looks to be moderately vigorous ... This is a tuff call? ---- Any other / better ideas out there..?