Should I maintain a friendship with a sister who is not from Ahl al-Sunnah, or should I cut ties with her?

A Muslim should not associate with people of innovation and transgression, except with the intention of offering advice and guidance, and provided they possess sufficient knowledge to do so. This is because a person is influenced by their close companion, and they may become an innovator like them. Therefore, one must be cautious and safeguard their religion.