To speak to what Accuracy said.... my D happened when my daughter 6 months old. It was all she knew, however, she did cry during exchanges, but of course, that ended. but they don't always miss the other parent. My daughter is 11 now and transitions quite well, she's been away with her dad for a week, and she facetimes to see the dog, not me, lol. She brags to her friends about how she gets two Christmas. It's not an ideal situation, of course, but they don't suffer as much as you think as long as you keep a consistent warm loving parental environment for them. Think about it, there are parents who travel for work a lot. Kid's miss that parent. Some work a 12 hour day. Kids miss that parent.

My ex married his affair partner. I am now friendly with her, we all do things together and I made sure (took a while) to make sure my daughter's well being came first, and she sees all of us get along and knows she is our #1. And I think it is the best gift we could have given her in this mess. Because of that, she is a very well adjusted, bright, friendly, kind-hearted girl who does not live a life of pain.

Just be that rock for her, and she will be OK.