Oh dear OP it sounds like you relationship with your daughter is getting very disfunctional, not helped at all by her father. I have two take always from this:
1/ Two wrongs don’t make a right, just because she behaves badly you need to take the moral high ground 2/ You are alternating between treating her like a child and then a complete equal. You both need to take a big step back on treating her as a child and demand more from her as an adult. To your specific post my responses would have been:
The other week She messaged from her room saying she got her exam Results but She had Failed and That she was so upset and doesnt know what to do.
me: I’m so sorry, you must be disappointed, let’s discuss it when I am properly awake (when it has all gone pear shaped is not the time to pull out ‘I told you so’ to anyone)
Anyway she fell out with me saying I wasn't showing I was proud she passed
me: honestly DD, I would have been more proud of you if you tried your best and failed than half arsed it and passed, but I am happy you passed as I always want the best for you.
Anyway she won't accept my apology and is giving the silent treatment saying' dad was right about you " I see right through you now" " you will never change"
me: silent treatment would get silent treatment right back from me until she behaves like an adult and articulates her grievances like an adult
she will hold a grudge for months and I genuinely have to beg for forgiveness.
Me: I don’t beg, i apologise, if that is not good enough then so be it, hold the grudge. I can only influence my behaviour not someone elses
I ask her to tidy-up after herself she says oh the other kids don't have to even though they are just kids she's 19 so then she will message her dad telling him I treat her differently
Me: Everyone has to tidy up after themselves appropriate to their age, so maybe they should be doing something. To her: I treat them as I treated you at the same age. I neither want nor need you input on my parenting of my own children thank you.
so I no longer ask her to do anything in the house.
me: oh hell no, rewards poor behaviour. Not only does she have to do it, there are consequences for not doing so.
she today wanted to rub salt in the wounds by saying her and her dad have lunch together on her breaks at her apprentiship.
me: oh great I am glad you have a good relationship with your father
Making digs like oh ill be giving my dad 600 pound of my wages to my dad to save and manage for me as he looks out for me
me: oh good that is a great idea. You could also just put it in your own savings account so you have total control which is best
I asked her dad to have her living with him but he ignored me email, I asked her to move in with her dad she ignores me,
me: I wouldn’t do that. I would not want her to feel unwanted by her parent. Also anything negative her father is aware of he WILL pass straight on to her and paint it as black as possible. Best as little contact with him from you as you can. I would say ‘I love you and want you with me but most of all I want you to be happy. If it would make you happier to move in with your father I will understand and support you’.
am I being unreasonable to think she's taking things too far and I'm not in the wrong to be upset?
me: you are not unreasonable to be upset, you are unreasonable to show it and to treat her like any other random adult rather than your beloved child that you want the best for despite her behaviour.