My mother in law has type 2 and she was very concerned about my daughter because she was drinking a lot and constantly eating. My mother in law (not having the best eating habits and being very much overweight) was constantly sneeking my daughter snacky foods all day long. Even though she had eaten lunch they would fix her a PBJ sandwich for example. Anyways, so I was very scared of the possibility because my side has diabetes as well so I just mentioned it to our doctor and she went ahead and ran the tests for it. I know it's hard because it's your neice but I would tell her mom how concerned you are and just advise her on the next visit to be sure and have it checked.