Is this wrong of me to talk to her one on one?

My so and his ex DO NOT get along there is a custody thing going on.

I noticed their daughter who I have to myself a lot of the time literally starting things between her parents. She's 5, and I know that sounds wild but believe me she does.

Let's say shes on the phone with her mom "dad makes fun of your phone all the time." And whatever else she can come up with and she snaps back and it's on speaker and we can all hear it and she is legit starting arguments between her parents.

Dad knows about it but didn't say anything, I told mom. I called her and I was like hey she is literally just coming up with things to get reactions out of both of you and idk what it is but that's whats happening."

And then when I was taking her to the park I was like "why did you tell your mom that your dad makes fun of her?" "I don't know. I thought it was funny."

So I said "Well, it's not funny. It makes them fight. Nobody likes to fight, it doesn't make anyone feel good and we should all be working together and being kind to one another, because we all love each other." And she sat there and stared out the window and said "okay, I understand." And hasn't done it since.

This is an example of some of the stuff I've talked to her about one on one and I'm wondering if doing stuff like that is wrong. I have just realised that when I get her alone one on one she truly listens and I've never ever used that to put anything bad in her head, mostly because that would be fucking evil. Plus, I'm pretty sure she tells her dad everything and if I had ever said anything wrong he would've corrected me.

I just need an outside input if it's wrong to talk to her one on one being her dads GF. My intentions are good though, but still. Check me

Ariana do you mean my so or his ex girlfriend/ child's mother (I hate saying baby momma it is aggravating)