No, the late degree rising has one of two possible meanings. The main one is that the situation does not have enough energy in it to provide an answer, usually because the answer is already known. The secondary meaning is that, because the ascendant is about to change signs, the situation is about to change.
It;s hard to say whether your sister-in-law feels remorse. Her behavior as you describe it suggests that you already know the answer to your question. Your sister in law, as the planet ruling the 7th house from the third house of siblings, is ruled by Saturn. Saturn has no essential dignity. Whether she feels remorse or not, she is not in a strong position as a player in your family drama. Saturn is about to be joined by Mars. If anything, I think your sister-in-law feels frustrated and upset. Obviously her life isn't going the way she wants. She doesn't seem to have diplomatic or coping skills.
You are symbolized by Venus, which is in detriment in Aries, so you are not in a good position to resolve this situation.
What you can do, is to stop focusing on how everyone feels (or imagines,) which just makes the whole situation overly emotional. Calm and rational heads will be needed to get whatever resolution out of this difficult situation the family can manage.