MIL issues

Hi.. not sure if i am overeacting or what but i feel so offended when my MIL wants my babyboy to call my SIL "mummy." Just bc her other grandchildren call her daughter by mummy. But my husband and my BIL are all called as Pak Busu (means youngest uncle) & Pak Ngah (means middle or 2nd uncle).. their sister is the only girl in their siblings and her children and my BIL children calls her mummy also. Thats why my MIL feels like my baby shld also refer her as that. But im not okay with it.. i dont call my aunties in that manner so i feel a lil bit weirded out.. and i feel like my motherhood is being snacth away.. the most annoying part is that my SIL was the one that asks me (infront of my MIL) what wld my son call her whether it will be Mak Long (means eldest aunty) or Mummy just like the rest are doing.. and i havent even got the chance to answer to ger qn, my MIL just interfere and said "Eh ofc la call u mummy.. why must he call u Mak Long?" Like hellooooo... then if thats the case can ur other grandchildren call me Mama?? I think she would feel pissed off if i were to do that to her.. It sounds like a small matter to people but i personally feel like this is hurtful to me.. esp when i have to go for emergency c-sect to birth my son and my recovery period is very difficult.. the whole journey is very rough and emotional for me.. thats why i feel offended by my MIL's remarks.. Or issit i am being overeacting or dramatic? 😞