I agree with dora830. Besides, grandparents usually are more patient and do more to teach grandchildren, and concern their health as well. Although they have different views of us, we can still talk and discuss. To maid, it's also difficult to request her following your instructions. If she did but maybe she's just 'kick one, do one'. You'll then be annoyed but can't punish her much. It's because your BB is on her hand in day time. Who knows what she'll do on BB. Fortunately, we can set up a cam at home and watch them in office. Certainly, there're good or bad grandparents, and also good or bad maid. It depends on our communications and luck la.
I also have argument with my mother ah, but it's easiler to flight with her rather than 奶奶.
How old is your son and that girl? My son also loves sweet drinks but I don't think it's the cause. My son's temper is also not good sometimes, but it's because he's similar to me ma. DNA, you know? Besides, he's now 17mths old. I read from book that BB at this age is 脾氣大上大落. Although it's a minor matter, they cry or laugh very much. They can't control themselves wor. It'll be better when they're almost 2years old. Of course, there're other problems when they grow up.
Just keep doing your best lah. As you said, your 奶奶 also loves your son so I think she'll understand.