Do I have a kinship ( رحم ) tie with my husband's stepmother?

If your husband's stepmother is a relative (dhāt raḥim), then you are obliged to maintain ties with her, and cutting her off is forbidden. The kinship (raḥim) that must be maintained refers to relatives from a person's own family, their descendants, ascendants, and their children, connected by a common kinship tie. If she is not a relative in this sense, then she still has the rights of a Muslim.