These are all excellent questions and you need to ask them of the orthodontist that will treat you. You might see your general dentist for a referral, and get an idea if in fact orthodontics is the correct treatment for you.
I do cconcur- I would advise seeing a dermatologist
I do not know why there are dentists that are still using the Sargenti method, I can only hope that the dental societies and the FDA are diligent in their efforts to ban the method.
I do not think it is serious but I think you should have him look at it.
I wouldn't be concerned at this point, at your next visit to her doctor have the doctor take a look.
It is difficult to give you an opinion without seeing it, I don't think it is serious but if it continues I would suggest you see an oral surgeon to get a definitive diagnosis.