baby mama drama

this may be long but I need some help.

I'm a first time "stepmom". My fiance has two kids. One 13 and one 4. Their mom lives in CA and their dad and I live in WI. Their mother gets them for the whole school year while their dad and I get them for a month and a half in the summer. Now here comes the messed up thing... when the kids are with their mom we dont expect the kids to live by our rules unless they are with us then our rules are ours. BUT their mom keeps calling the oldest to tell her what she can and cant do. the young one is young so what we do the little one does. I dont mind if the older does whatever their mom wants but when they're with us their mom shouldn't be invading. I feel like she is invading privacy and doesnt get the point that our roof is ours and her roof is hers. Could we talk to the lawyer about this? is there anything the lawyer could do to stop her? I mean I know they are her kids but for her to keep checking in feels like she is invading. Every morning is a fight with the kids now.

Their mom doesnt let them eat meat except for Turkey and chicken. and no white rice. The little one loves eating what we cook but the older one is always telling her mother and then she calls and tells the kids to not eat what we eat. The older one loves eating what we eat too but because their mom put words into their head they resist. It's very frustrating to have to obey their moms rules while they're here.