Regardless of the diagnosis, your acquaintance has obviously benefitted from the use of insulin. This is reflected in the excellent control shown over those years. Many T2s use insulin, and it is prescribed earlier in the treatment cycle now than previously. Were I your acquaintance, I would continue with the insulin. It is quite possible that because insulin therapy was begun so very early, years of frustration with medications that don't work as well as the hormone were avoided, as were possible complications of poorly treated T2.
Jen
Jen