Not much you can do since she's an adult
Dear Prudence,
I don’t know how to handle my daughter anymore. Her brother is eight years older than her and joined the military at 18, so she was used to being the only kid for a while. When she was 14, a family tragedy happened, and my husband and I ended up adopting the infant. I didn’t expect my daughter to be all sunshine and roses about the situation, but her moodiness has morphed into a real mean streak.
At best, she ignores her little brother, and at the worst, she complains and calls him “it” as in, “Why can’t I shut it up” when he is being loud and playing. She will not lift a finger if the favor involves her being around her brother. We are not demanding that she babysit every day, but it is ludicrous that she can’t get groceries out of the car while I am trying to wrestle a cranky toddler.
My husband and I finally had a serious talk with our daughter because her behavior is only getting worse. She exploded and started ranting about how she wasn’t “consulted” about the adoption, she didn’t want a little brother, and would never consider him family. My husband snapped that she was acting utterly selfish, and she wasn’t a queen who could give out commands. This was her little brother, and whether or not I had given birth to him, it doesn’t change the fact.
Our daughter stormed out and was gone for several days, and didn’t tell us where she was. She graduated from high school last year but has no motivation toward continuing her education or finding work. People just kept telling us this was normal and suggested we gave our daughter a chance to adjust. That isn’t happening. So what now? It is starting to negatively affect our son.
Re: Not much you can do since she's an adult
In ALL of this you're talking about how she acts, how it affects the little brother. What about how at early teens suddenly what she expected was flipped upside down? Get yourselves to a therapist too. You likely had great intentions but failed your offspring.