Is it obligatory for my friend and her family to maintain kinship ties with those who assaulted them and forced them to leave their home and city?

It is established that maintaining kinship ties is obligatory, even if they sever them or mistreat you. There is a great reward for the one who maintains these ties with Allah, and it does not diminish their dignity; rather, it elevates their status with Allah and among people. This might even lead them to reconsider their estrangement, for Allah Almighty says: ﴿Repel evil with that which is best, and lo! he between whom and yourself was enmity will become as though he were a devoted friend.﴾ (Fussilat: 34). They should also be reminded of the seriousness of severing kinship ties.