There are a few signs that may indicate that a child is being alienated. These include:
The child suddenly starts to have negative feelings towards the other parent without any justification. The child may make up stories or lie about the other parent in order to make them look bad. The child may refuse to spend time with the other parent or have no desire to see them at all. The child may also try to distance themselves from the other parent's extended family and friends.
If you suspect that your child is being alienated, it is important to talk to them about their feelings and try to get to the bottom of why they are behaving this way. If you are able, it may also be helpful to seek professional help in order to address the issue and help your child heal any underlying emotional trauma.