Type of diabetes

hi guys I've not been here for a while..
I wanted to ask a question about being diagnosed with type two diabetes and then being told it might be type one diabetes? My sister has been told that. She has metformin and glucose levels are near in control. So now her doc has referred her to c a nurse n said maybe she is a type one like myself..

Sorry I wrote that wrong - I meant not in control

Is it just a blood test that they will do? It is the diabetes nurse she will be seeing