BBK, any chance there's some Aspie in there with Tink?
I've only skimmed the replies, I'm not well enough to sit at the computer for too long at a time. So forgive me if I repeat what others have said. I did see that you have had some good advice already.
The insistence on the new way being the way it always must be done - you get into "habits" after just one experience, especially with Aspies. For example, ONE day, for a treat, I decide to buy a slushie for difficult child 3 after the beach. So next time and every other time afterwards he then says, "But you ALWAYS buy me a slushie after we go to the beach!"
He understands now, but will still ask. He's finally learned that if I do it once, he should be grateful. If I do it regularly, it still isn't a promise to do it every time. I also use logic - if it's a scorching hot day AND I'm feeling generous AND I happen to be somewhere that I can buy a slushie, then I MIGHT buy him one. But at the expense of any other treat I might get him.
You've not been picking your battles. You've been avoiding all confrontation. As a result you're teaching her that the world revolves around her. So is it any wonder that she is taking all your generosity as her right?
She needs to be reminded that you are making concessions. That means with dinner, you cook what you want to cook. However, plan for something else to be available, if she really hates chicken. I had problems like this with easy child 2/difficult child 2 - she is very faddy with foods, I hadn't realised just how much a slave I had become to her faddishness, until she moved out.
However, I would be swayed by her tastes but not totally controlled.
difficult child 3 - he will eat bolognese sauce in various forms. It can be used to make nachos (the way our family eats them, which is my invention to make sure he gets enough meat) or can be eaten with pasta. Or I could turn it into chilli con carne. I always have some in the fridge and more in the freezer. Then I will cook what I want to cook.
Our rules with meals - I cook what I want, but difficult child 3 has to have a taste. He then has to say something he likes about it and something he doesn't like about it. He needs to explain himself in ways that are acceptable and ways we understand. He can then eat what he chooses to. This tactic was brought in by BF1 while we were all travelling around NZ in 2007. I love to try the foods of an area, to buy the local produce and eat the meals the locals eat. And in NZ they eat a lot of kumara (orange sweet potato). BF1 LOVES kumara and used it to make a number of different dishes. difficult child 3 tried them, BF1 made him describe the taste and texture and then he was permitted to eat something else. A lot of the time, difficult child 3 decided to eat more of the food he had previously said he didn't want.
Something I found with easy child 2/difficult child 2 when I involved her in meal planning, was she was imposing her tastes on the whole family. She mightn't "hate" chicken, she just might prefer something else. But given half a chance she was trying to avoid chicken because I relied on it a lot, and she always got fed up easily with things she had frequently. If I just went ahead and cooked chicken, she'd happily eat it. Or maybe grumble a bit, but eat it.
When she got particularly argumentative about it, I gave her the job of planning and preparing dinner. The rules are: it can't cost any more. It has to feed the same number of people. She has to prepare it all herself, including shopping for it, acquiring it, cooking it and serving it.
For example - it's all very well to say, "I don't want roast chicken tonight, I want lasagne," but it takes a lot more work to make lasagne. If she wants it badly enough, she will make it. In the process of making it, she will realise just how much she is asking of me.
Christmas ornaments or anything for the house - that is YOUR choice, you are entitled to buy what you want. If she is expressing dislike for ANYTHING she needs to be able to say why, with a good reason. She needs to be able to say, "I don't like those ornaments, I think they're too garish, the pattern is too large and seems out of character."
She should NOT say, "Don't buy those, they're disgusting." It doesn't really convey anything.
It's all a compromise and communication is an important part of the key. She has to learn to get on with other people in the world, part of this is learning how to communicate effectively and positively with people.
I use the 'flatmate" principle. After a certain point I treat my child as a flatmate. The child has to learn to get on with everyone else in the house, as if she is sharing an apartment. General courtesy applies, as does consideration for others, pulling your weight (financially as well as with chores). Some mutual compromise is needed, but part of this is, when you're wanting a meal that you know she doesn't like, you have available for her (at her choice) something she can eat instead.
Showers and personal hygiene - we will tell them when they're stinky. There has to be a good reason for not showering (no hot water, for example). We still strongly recommend an underarm scrub with a washer and then application of deodorant. When clothes are stinky because the child is stinky, then the child must wash their own clothes. We have a bottle of vinegar in the laundry, all sweat-smelly clothes put in the laundry must have vinegar splashed on by the clothing owner. If the clothing still smells when it's been washed and going on the clothes line, then the owner is called and made to take care of it themselves. Failure to do this results in them being ostracised by members of the family. In extreme cases (difficult child 1 at various points) he had to wash his own clothes in a separate load. Nobody else would allow their clothes to be washed with his. I was happy to teach him how to successfully clean his unbelievably smelly and dirty clothes and I think being told by the others in the family that they didn't want their clothes washed with his, was a nasty wake-up call.
The opposite sex can help - difficult child 1 did shower a lot more when he had a girlfriend. His wife makes sure he showers a lot. difficult child 3 isn't always aware when he's stinky, but we have certain rules and they include the need to wash regularly. He will sometimes try to avoid a shower if it's late at night and he's tired, but lately I've been insisting that he shower as soon as we get back from the beach, for example. If he showers after an afternoon beach trip, then he doesn't have to shower later at night.
Use commonsense, use the need for her to compromise and consider others. Make her explain her objections and ANY choice that affects other people, then the wishes of others must always be considered also. If you always want A for dinner and she always wants' B, then logically you should take turns having what you want.
She needs to learn compromise. Otherwise you're only making the situation worse.
It's not "Explosive Child" that says, "give way all the time". It is all about compromise and allowing the child SOME control where appropriate.
You take from it what you can use and leave what won't work for you.
I hope this helps.
Marg