I'm watching this blending going so early on right now with exW and her new bf. I think they've made it past the 3 month mark and have blended the families as if they've been together for years. It is quite shocking and concerning to watch. I don't have any control so I can't do much about it. All I am doing is being super solid for my kids and making sure they're good.
They both did this precisely for themselves so that they could spend more time. She told me her rationalization for having him meet the kids so early on and I call it baloney. It was about her and him, and not the kids. Which also makes me concerned when it comes to the bf - his judgment is suspect. Knowing his past marriage and what happened, both seem to be wanting to fill a void in their lives and it's clouding their judgment on what's best for the kids. I am super annoyed about it and I am watching the kids very closely.
If they break up, this is going to have an impact on the kids for sure. They're pretty attached to his kids and have gotten used to having him around. I wanna smack both of them across the heads to bring some sense to them but it's already too late. ExW is selfish and impatient and the kids will pay the price for her actions.
So, I concur with everything Don said, and others that have cautioned you against changing up the timeline. I think you should have a honest convo with her rather than brushing off her comments because that comes across as dismissive. If she doesn't like your stance on this then that's her problem.