I must admit I am very lucky with my Inlaws... they love me and my daughter as thier own. Mum is always on my side and ever ready to defend me against her son ....
I know how are you feeling a firsttime mother ?(are you) Grandmother always think they know more about us cuz they been there.. And they think thier ways are better than other as far as beeing a mother is concern (and same to you, you think your ways are better than her). Try to control your temper as much as you can and try to mix your ways and her ways to make a better harmony.