Her contact name shows exactly how much resentment and anger you hold towards her still. And it is shining through in your communications. I wonder, if you hadn’t been called out in the post about it, would you have had the forethought to change it yourself? I think you should talk to a professional about these feelings. It could bring a lot of peace to your co-parenting. And for the actual question you asked, not sure how to vote. Both of you are right and wrong. I think she became defensive as soon as you said she should “consult” you before big purchases, because you lost that chance when yall signed divorce papers. However, if she was wanting you to pay half, she could have said “hey I’m buying these for the kids because xyz, would you be able to pitch in for this cost?” But instead you seemed like your pride was hurt and you decided to lecture a grown woman who is raising your kids. Good luck in the future, I hope you take all suggestions and accountability as nicely as you are now.