Unfortunately my DS1's SM was an abusive bitch, who thankfully my Ex has finally extricated himself from - she is about to lose custody of her birth DC's because she IS actually abusive.
However - I'm not against ALL SM's - DD's SM is a bloody ANGEL. She's never stepped on my toes, yet is there to listen when DD is being difficult, has gone out of her way for DD repeatedly, and is an all round bloody STAR.
But she has never reported me to SS, or told me that I'm not allowed to speak to my Ex about DD (which DS1's SM did, she insisted that all communication about DS1 went through HER), or tried to attend parents evenings (DS1's SM wouldn't 'allow' his dad to attend DS1's parents evenings without her), or threatened to stab me over me not giving her a bottle of headlice lotion (which DS1's SM did, she wanted me to pay to treat HER child when he was the one that was causing DS1's repeated infestations - she wouldn't treat HER son unless I paid for the lotion!), she's never threatened to punch me at a sports day (Which DS1's SM did because at the picnic lunch, DS1 wanted to sit with both me AND his dad, so we suggested setting up the picnic blankets next to each other, she went nuts and refused and then threatened to punch me if I didn't let DS1 sit with them for the whole picnic lunch) she's never stopped contact by telling DD's dad not to see her, which DS1's SM did, and most of all, she's never hurt DD, unlike DS1's SM. Who he thankfully has no need to contact any more now that his dad has finally left her.
Instead she has been a helpful, listening ear, communicates well with me, knows when to step back and allow my Ex to deal with a situation, has been there as a friend to DD when DD has needed it, and the same to me, I wish DD's SM had been MY SM, she's so wonderful!
Not all SM's are lovely, just as not all mum's are lovely (I HATE HATE HATE the term 'birth mum' unless used in conjunction with ADOPTION.) I am my DC's MUM, not 'birth mum'. I always have been, always will be.
Why do SOME SM's try to take away that a Mum's title is Mum?!
You have a Mum and a SM, don't try to change that to anything else, THAT'S what pisses off a lot of Mum's that have to cope with less than perfect SM's - and using a term like 'broth mum' to describe a MUM is just one sign that a SM IS trying to redefine the Mum's relationship with their DC's. Which could be a good indicator of WHY you may not get along with your DSC's Mum...