Does she have to sit with her sister’s husband and talk to him?

No File Exists
Check below answers in case you are looking for other related questions:
Can she uncover her face in front of her sister’s husband?
Ruling on covering the face, with detailed evidence

No File Exists
Related Answers:
He studies in a mixed environment and when he interacts with his female classmate she doubts his actions
He told his Hindu girlfriend that he would give up his religion; what should he do?
He regrets his first marriage and wants to take a second wife
Can she uncover her face in front of her sister’s husband?
Ruling on covering the face, with detailed evidence

Recommended answers for you:
Qaseedat al-Burdah by al-Busayri and an explanation of what it contains of kufr and heresy
Does touching the penis invalidate wudoo’
The ruling on plural marriage and the wisdom behind it
Keeping a dog, touching it and kissing it
Are there any types of seafood that Muslims are not permitted to eat?