I'm not sure if this is more about the teenage stepdaughter, or SO.

SO has 3 kids, SS14, OSD13, and YSD10. This particular issue is about SO's relationship with OSD. OSD's attitude and outbursts, according to SO, are evolving more and more to be like like BMs and it is very off-putting to SO, but I don't think he handles it well. I have noticed a lot more bossiness with siblings, "whatevers, i dont care", and a nastiness to her attitude when she doesn't get what she wants. 

SO's birthday is coming up and BM has agreed to let him pick them up after school. OSD said SO told them last week that he would be out of town and might not be able to pick them up. I have no idea why he would say this, because the plan was always to pick them up, we've been talking about it for over a week! OSD tried to clarify this with SO because she needed to let her coach know if she would leave early... but as a 13 year old, this is a major inconvenience, so imagine an annoyed teen saying "So are you going to pick us up? Do you even want to see your kids on your birthday?". SO could have easily just said, yes, of course I want to see you guys... but instead he said in his own fed up tone, "It's ok, you don't have to come if you don't want to". There was a little back and forth but pretty much repeating the same things. This isn't the first time he's responded this way. 

I shot SO a look and interjected, "Yes, he's picking you guys up". After they left, I scolded SO, that I didn't understand why he was talking to OSD this way. She is not an adult, she is a teenager (barely). He said he was fed up and he didn't want to deal with her attitude anymore. I told him that not dealing with it is his problem.. he has never dealt with it, he'll just ignore it and choose not to interact with OSD if she's being unpleasant. We ignored each other for most of the night while some friends dropped by.

After the friends left, he came back to ask me if I was still mad. I said yes, I didn't like the way he was treating OSD and, the way I see it, he was treating her like she was BM, and that is unfair. If he treats her like she is BM, she will become BM. I told him he should not be giving the kids the option of not coming just because he is arguing with them. Lastly, I told him that OSD is a teenager, she is going to act disrespectful sometimes, but that doesn't mean he should go lower. Afterwards, SO understood and said he would talk to her. 

This morning, before I left for work, I suggested SO send her a text, maybe she would appreciate it. He got upset that I was bringing it up and said he would talk to her. Then he said I was treating him like he was a bad father. I said I was giving my point of view of what I would have appreciated from my dad when I was a teenager. We just left for work after that.

Did I push the issue too much? Was I wrong to say anything? I know I can't control their relationship, but I'm going to point out to SO if I think he's messing up.