Am I out of place for wanting to be involved in fiance's kids parenting

I really want another perspective I'm not looking for whether I'm right or wrong.

I'll start out with how I got with this man. He has a 4 year old and a 2 year old we've been together for a year and a half now.

He cheated on his ex with me for a long time, I knew the whole time I didn't care I was really selfish back then. At one point I made him choose me over the girls we moved away and I thought I was about to get my happily ever after

But I was diagnosed with lupus two weeks into our move. We both did alot of soul searching we ended up moving back to our hometown for better treatment options and to fix our problems with his ex.

She has been very graceful about everything but she is firm when it comes to keeping me out of decisions with the girls. She got married, has a set of twins now one being disabled so we asked for joint custody to help out but it was my idea so she shut it down.

She has the oldest in dancing classes that I don't think is appropriate in her young age plus it cuts into our visits.

Recently she approached me and asked me to stop making demands or suggestions. She feels like I can very easily manipulate my fiance, she called him my puppet and she'd meet him halfway if that's what he truly wanted.

I think that is such crap, she may see me as trash but I can help her that's all I want.