Find out if she is being influenced by a cult. Is it called RSSB? Satsang Beas? If she were in India, her interest might be one thing; but over here it is another. Find out what appeals to her about Sikhism: is it the lack of morals and rules or is it the morals and rules? They have some tight rules but who is their magisterium? It could all change tomorrow. Young people from our country frequently try to escape the rules of their own religion, only to take on those of another religion, less grounded in a solid theology.
If they talk about saints, it’s not the Catholic saints although they throw in a few of ours to confuse things. If they have references to Christ, He is just considered one of the many “ascended masters”. They are kind of “mystic”-based which means you can get pretty lost in your own ideas and meditation.
Read about Sikhism. Also Google “Sikhism and Satsang Beas”. This is a very popular group for young people who are curious, who like something exotic, and yet feel a sort of familiarity with their Western references. There is a lot of meditation. No alcohol or drugs. Clean living. Marriage centered. Lots of good ideas mixed in with some strange ones. Add a few yogis, a few amazing stories. Not Christ-centered. kind of an amalgam.
Try to learn more about it than her.