>>Being a Catholic is she obligated to follow the pope’s ideas on immigration?<<
No, but she is reportedly a “fervent” Catholic, and if she believes this Pope to be the true Vicar of Christ, she may be reluctant to take a position that is contrary to his teaching. And that would be a very bad consequence of her being selected to sit on the Supreme Court. Also, her adoption of two Haitian children strikes me as virtue signaling at its most egregious, given the fact that there are thousands of orphans in need of parents right here in America.
With regard to immigration, the Catholic Catechism places the responsibility on immigrants to obey and respect the laws and culture of the host nation. Whatever Bergolio says on the matter is quite a bit less relevant.