How do you handle schedule changes when your ex is being difficult about it?

I switched my Wednesday pickup to Friday because of work stuff and asked my ex if that was okay. She agreed but then told me I'm being selfish and not prioritizing my kids. But the Friday arrangement actually means I get them the full weekend which is better? I'm genuinely trying to make it work and keep things consistent but every time I ask for anything she acts like I'm abandoning them. Do I just accept that I'm not allowed to have any flexibility or what?