What's in a name? Bio-mom vs Step mom

I started a little debat on my facebook last night by asking for suggestions on what my bonus kids could call me besides my first name.  I didn't mean to start the discussion but it was very intresting.  One of my good friends who is a counseler (a very good one) gave me some good things to think about and I want to pass some of that along because I agree with it.  The bio mom is extremly against the girls calling me anything but my first name---expecially mom.  My counsler friend explained that it's not about the girls calling me mom. It's about her trying to prevent them from loving me.  This is just the current battleground for her.  If I give in and have them keep calling me Jamie then she wins this round but will find another way to block them for loving me.  I have not insisted they call me mom yet but let them know it was ok.  But bio mom threatened them to never do and they are scared.  I don't want them in the middle.  But my friend pointed out they will always be in the middle a little because of the bio mom's hatred towards me.  I read something on the wicked step mom blog about the bio mom calling bonus mom saying that it hurts in feelings that bonus mom was volunteering her time for a school play.  This has happened several times to us.  I volunteer each week (in a town 45 min away) so my kids have a parent in the classroom.  Studies tell us that kids do better in school when their parents (bio or bonus) are consistantly at the school.  Bio mom works and is unable to.  I understand that might be hard for her.  But her response was to try to get me kicked out of the school and crying about how "hurt" she is and claiming she will bring it up in court.  Yes, court.  We all know she will be laughed out of court if she actually brought it up in a bad light since it good the kids. But it's about her fears of not being a good mom.  Doesn't she know if she allowed all the parents (4) to be part of the kids life, not only would  their lives be better but her's would be easier.  Being a divorced working mom doesn't make you a bad mom.  Not allowing the dad and bonus dad and bonus mom to help and be part of things does make you a bad mom.  So I still haven't decided what to do about my bonus mom title but I am definatly going to talk to the kids and after the decision is made then tell bio-mom. She should fight with me not the kids.  Silly insecure woman.  Kids can love so easily.