Is mom free to talk to SMs kid's teachers? Go to her kid's conferences? Attend SM's kids doctor's appointments?
Shouldn't stepmom just appreciate that this person loves and cares for her kids and let her go with her if she believes she should be going to mom's kids appointments and such?
Mom does have a connection to SMs kids, a similar one that SM has to mom's kids. Sm is connected via dad and mom is connected via her children . It's like the six degrees of Kevin Bacon, only we'll replace K. B. with "other people's kids" ...
So it isn't about that, it's about the love that mom might be trying to show to SM's kids, folks.