MiL is called Ma by her doting sons. It really grates, not sure why. Now my 5 year old DD has picked it up and calls me it constantly, Ma this, Ma that. I've asked her to call me Mum but she keeps reverting back, so now our conversations start 'Ma' 'mum' 'sorry, mum. Mum, Ma, mum I meant argh!' AIBU and way too controlling?! Should I just force a smile and hope this will pass? Or should I stand my ground and escalate the correcting to not responding to all Ma references for as long as it takes?!