Reply to My older daughter is not nice to her much younger sibling (14 years apart). I...
Joe

Is she the oldest? Was she the only child before the sibling came along? If that’s the case, I feel she resents the attention the younger sibling gets and sometimes they get jealous of them. But you may want to set aside special Mom and daughter day and go out together; just the two of you and spend some quality time to get to know her at he stage in age. Read more about teenage behavior because it’s also their age and the stage they’re going through. Trying to figure out where they fit with others. But just try to set time aside just for her. Her reasoning development it’s not fully developed until past 18. I’m speaking from experience. My daughter is 18 now finishing her 1st year in college and it’s been a great change in behavior towards her younger siblings and towards us as well. My wife started giving her special attention and going out just with her and it helped a lot. I hope this advice would help your situation.