I'd love to get some feedback on this. I'm wondering if my SD6 has an unhealthy attachment to my SO, her father. I probably sound paranoid, but her behavior is increasingly unsettling.

Background:
her parents divorced when she was 1 1/2yo. I came into the picture just after her 2yo birthday.
I moved in with her father 8months after that so she was a little over 2 1/2yo.
So I've been acting as co-parent/SM since she was 2 1/2yo
we have 50/50 custody

So, her BM is not the most loving, present person in her life. My SO, her father has really been the primary parent he entire life. He researched the preschools, he researched her elementary school and fought for he to be in our district which is a better district, he coordinates all of her activities, he takes her to all the bday parties..even when it's the BM's weekend, because she won't do it. BM has been pretty checked out. She treats her daughter as more of a niece than her own daughter. She sends her to school with a just a breakfast bar. She never reads to her, she never attends school meetings, kindergarten graduation, anything!

My SO/her father is way more engaged and together we've created a nice, loving household in which SD prefers to be with our house than her BM's. She cries when she has to go back to BM. But even though I have been her SM for the past 3+ years, she practically ignores me and is highly daddy-centric.

Some examples: My SO/her father works here at his home office, so on the weekends when he is working for a few hours, she has to be with him instead of simply playing with her toys or entertaining herself. When he goes out for an errand she cries if she can't go with him instead of simply staying home with me. She treats him like her playmate saying that he hurts her feelings when she is upset. When I ask her to clean her room, she does it all by herself, no problem. But when he asks her to clean her room, she cries and demands that he helps her. They often take naps together and he falls asleep in her room at bedtime after reading stories. I need to say that there is absolutely nothing sexual happening with these things. I find it necessary to say that because society is so (understandably) hyper-aware of that. They are really two peas in a pod. She is his shadow much of the time, and clings to him, constantly kissing him, hugging him, wanting to sit on his lap, to the point where I know it even annoys him. When we have dinner she has to sit beside him and immediately sits on his lap after she's done.

What I find unsettling is that she is not allowing space for a female figure in her life..whether it be me or her BM. She constantly interrupts when my SO and I are having a conversation, even though we tell her to wait her turn. When I pick her up from school, her first question is "when is daddy coming home?" Whenever I've tried to do things, like play games, color, go on walks, etc, she last for about 10minutes and then wants daddy. Reminder: I'm not a newcomer, I've been in her life for 4 years since she was 2yo.

The big thing now is she is beginning to lie/cry more to get sympathy. She once told my SO/her father that I pushed her..an outright lie, I would never push anyone, let alone a child. She also told me that she doesn't like to go to her mom's because she shouts. When I asked what she shouts about, she said she shouted at her to not go too deep into the water when they were at the ocean...a totally reasonable parental request. When I asked her what else, she couldn't think of anything. Even though her BM isn't the best mom, my SD has learned that she gets sympathy from daddy when she pits the two against each other...or even us.

I'm concerned that she may have an unhealthy attachment to him. I see other girls her age and they don't act like this with their fathers...not to this degree. I'm more concerned about how this is going to play out when she gets older. Of course the same old story..when I try to bring any of this to my SO's attention, he's immediately defensive and we can't even talk about it. I'm beginning to cringe whenever she is here. It bums me out because it could be different, but he won't address it out of guilt.

thanks for reading...any advice or comments?