What is the ruling on my going with my husband's sister to perform Umrah, knowing that my father is present and visits me? Is his presence necessary in this case?

It is not permissible for a woman to travel a distance considered a journey unless accompanied by a mahram, whether the journey is for Hajj or Umrah. The intended distance of a journey is a day and a night's travel or three days' travel. Every distance that is called a journey is forbidden for a woman to undertake without a husband or a mahram. A mahram is an adult male whom the woman is forbidden to marry permanently due to kinship, suckling, or affinity. Being your wife's sister does not make you a mahram to her, nor is your father a mahram to her.

Therefore, it is not permissible for your wife's sister to undertake the aforementioned journey unless this Umrah is the obligatory Umrah. In this specific case, many scholars have permitted a woman to travel with a trustworthy company.