You stated that you want more say in your childrens lives, but have you seen a solicitor to find out what your rights are? Or the Citizens Advice Bureau if you can't afford the fees. She is not playing fair and she knows how to get her own way with you - in fact I would go so far as to say her communication is bullying. I'm not saying start a legal battle here but just start standing up for yourself - that means acting in a dignified way not starting to get into childish bickering.
I hope you have been keeping a record of all her correspondance? I would just ignore her text, it warrants no reponse. YOu have already explained the situation - remmeber you will never win with her in her state of mind at the moment. I would simply forward the letter onto her. And find out your rights in regards to your kids.
