The bottom line is if there is no visitation order established she doesn't even have to let the father have visitation...much less you...or be around the child. Get visitation established FIRST...the worry about the rest...
On a personal note...I am a step mother, and a mother...and my children will sonn have a step mother.
Stepmother sometimes get the short end of the stick...but if you do what is in the best interest of the child that is all that matters. Do not try to discuss matters of parenting with her....while you may love the child it is not your place....it must remain between the parents. Now if she invites you to take part that is different. But be courteous and let Dad handle mom. I have found that if you hand it over and just support them from behind the scenes life is much easier for everyone involved.
I know it is hard with someone who is very contolling but the more you try and "mark your territory" the more a control freak will dig their claws in.
Good luck to you...and have Dad get visitation established pronto.
Oh and by the way....when my ex husbands wife said I couldn't pick up the kids...he asked his attorney about it....see we are at a big geographical distance and my husband is active duty. When he was going to go get the kids he was put on duty and wasn't allowed to leave area. He asked if I could come get them...she said nope. We figured there was nothing we could do, but we contacted attorney...he called her attorney and I was told to go get them...so I did.
Long story short...I don't know why but Oklahoma would hold her in contempt if she didn't allow me (wife) to get kids...she owuld have been held in contempt for denial of visitaion. Maybe its because he is active duty....
Good Luck