Where to put step mother of the bride

My dad’s girlfriend (they have been together for 14 years). Is an amazing lady, I consider her as my step mom. So I wanted her to walk down the aisle after my mom. And sit at the first row 2nd seat. In My mom threw an tantrum because in my moms opinion she should have the aisle seat and should walk down after my step mom because she matters more and is one of the most important people at the wedding? What can I do ? I wanted my dad to have the aisle seat. My step mom next to him then my mom 3rd over here’s a picture of our ceremony site for reference