Let me preface this that my response is based solely on my own parenting experiences and, thus, may be completely off base for you. Take it for what it's worth.
she insists on going to school without a coat while it's freezing, we argue, and she throws the coat back into the car and runs up the school steps.
My daughter used to fight me tooth and toenail on wearing a coat or what I deemed proper attire for the occasion - whether it was a nice dress for church, a coat for cold weather or a top with buttons (she went through 3 years where buttons of any sort created melt down). How I wish I'd known to have her tested for sensory issues. She is now an adult and has told me that she vividly remembers those battles and that all the while she was feeling bad for misbehaving, the panic over having to wear something that made her skin crawl was worse - and that she had no idea why I didn't understand that what I was asking her to do was so unreasonable. She thought everyone felt that awful in their clothes and thought she was the failure for not being able to handle it.
She'll insist on a bath while we only have time for a quick shower, resulting in a meltdown and drawn-out bed time.
Both my daughter and my youngest son would rather go dirty than take a shower - again the sensory thing. The feeling of the water pelting on them is torture, whereas a bath is nice and soothing. Using soap or shampoo? That's a whole 'nuther battle.
Because of having a better understanding now of why there is resistance to certain textures or experiences (like showers), I actually have changed my parenting a lot with the youngest. If we're running late, I'll let him skip the quicker shower at bedtime with the bargained agreement that he get up early in the morning to get his bath. He will actually set his alarm to get up early in order to have his bath rather than take the shower. And to me, it isn't a defiance/disobeying issue - it is about helping my child figure out how to make compromises and workarounds that allow him to cope in his own environment.
When he argues about setting the table instead of playing Minecraft? Yeah - no mercy at all. First argument gets the Minecraft gone for the rest of the day.
Anyway - this may or may not apply, but I wish I'd have had some idea that this is what was happening when my kids were younger, so thought I'd throw it out there.
