What is the ruling on escorting one's sister to a neighbor's house if it is highly probable that she will engage in backbiting, and is the escort considered a participant in the sin?

If visiting neighbors is for the purpose of discussing forbidden matters like backbiting, then it is impermissible to take one's sister there, as it constitutes cooperation in sin. However, if the visit is for a permissible purpose, but there is a possibility of backbiting occurring, then taking her is not forbidden. Nevertheless, she should be advised by explaining the prohibition and danger of backbiting.