Did the questioner commit a sin by supplicating against her husband's brother's household and their daughter due to the injustice she experienced, and will Allah hold her accountable for that, knowing that she was in a state of anger and did not intend to harm them but rather to ward off their harm from her?

Forgiving an oppressor is among the best acts of drawing near to Allah, and its reward is incomparable to the fruit of vengeance. Supplicating against an oppressor is permissible to the extent of their injustice. If you exceed this limit, or supplicate against someone who has not wronged you, that would be an injustice requiring repentance. Since seeking their forgiveness might lead to animosity, it is sufficient to supplicate for their good. A penitent person should have a good opinion of their Lord and beware of despair, for Allah forgives all sins. Anger does not negate religious accountability as long as the angry person is aware of what they are saying.