Need some help or at least validation
Long time reader, first time caller.
I'm going out of my bloody mind over here. My partner and I have been together for 4 years and lived together for 2. The first year we lived together, everything with the kids was rainbows and unicorns. I got on with his daughter (17 now), he and my son (15 now) got on like a house on fire, and they got on together.
After a horrid family trip where SD basically shape-shifted into a monster (literally threw a toddler temper tantrum about not being able to go to the holiday carnival in the middle of Hyde Park). When we got home, her punishment was going to a long process of earning respect and trust back. Needless to say, my SO is a complete pushover with her and she got all her privileges back in about 1/6th of the time we discussed. From that point on, she's been unbearable. Talks back, whines, eats like a toddler, forgot her manners entirely, doesn't hangout with my son anymore, fights me on everything, threatens to SO that she doesn't want to live with us anymore, has to be reminded to do anything (especially chores), and is so inconciderate and rude I dread serving dinner and am dreading Christmas with no thank yous and the inevitable complaints.
Obviously he feeds the monster because she doesn't get punishment for anything, gets whatever she wants (literally you name is she has it-- including a brand new car), doesn't get told off when she talks back, and basically has him wrapped around the axel that she'll be depressed if he doesn't make her happy. On top of this, because I had pointed out things she's done and not done, my SO has now taken to nitpick on everything my son does and tattle tail everythign he doesn't like to me. It has caused some real big fights and a pretty general issue with us. I dread her coming over, but now I'm starting to feel I'm on eggshells when my son is over too.
After reading around this forum, obviously I've got a Guilty Father and a Mini-Wife on my hands. I'm just at a loss because talking about it with him gets me no where but fighting and animosity and accusations that I don't 'like' his daughter. Trying to talk with her is PURELY useless. I've tried to just disengage where I can, but it's maddening to have such a good relationship being torn at the seams by teen angst and poor parenting choices.