Is it permissible to visit a relative who belongs to a Sufi order and return her gift, knowing that she is a first-degree relative, for fear of severing kinship ties?

Exchanging gifts among Muslims is desirable and encouraged in Islamic law, especially for relatives. It is part of the Prophet's guidance (peace be upon him). Rewarding your relative for her gift is a good thing, even if she follows the Sufi path. There is no harm in visiting her, as long as the visit does not lead to any religiously prohibited act. If she practices innovations in Sufism, it is advisable to counsel her with wisdom and good admonition, while being cautious not to rush into declaring someone an apostate.