While I'm not super familiar with ich's presentation in a regal tang, something about those spots looks a bit ... fuzzy ... to me. @melypr1985, @Humblefish or @4FordFamily may be able to offer a bit of clarification. Spots do look too large and too few for velvet - which is a good thing.
If it turns out to be ich, you'll want to use copper (I use Coppersafe) in a quarantine tank. Regal tangs are sensitive to Chloroquine Phosphate (CP), so that would be something to avoid. All of the fish in the tank she's in will need to be treated, and if that's your display tank (liverock, corals, inverts) then it should be run "fallow" - without fish - for 76 days.