I'm a stepdaughter to two people and honestly just try, go with it. Don't put an labels on you or the kid, you're a parent, they're the kid. Do parent things. Care for them, raise them, teach them maners and spend on on one time with them. Sometimes I feel like I love my stepfather more than I love my father just because I know how hard it must be and how hard I know he's trying. And for the 'just existing' thing I'll tell you right now she feels the same way. Me and my stepmother are either screaming back or just existing. She probably knows you're not happy with her and that shit stings.

I'm not saying you're a terrible parent, but you do need to grow up a bit. Building a relationship isn't her job, she didn't join your life, you joined hers. If you want a relationship with her then work toward building one.

I have two stepparents, one who is my favourite parent over my biological parents and one who is the only person I've ever really felt hate towards. I know a fair bit about the relationships and woud be up for answering any questions, but mainly just built a relationship. Read her favourite book or something, that's the first conversation I remember enjoying the company of my stepfather.