Her daughter did nothing wrong even by your standards. You seem ready to judge her without knowing anything about her. Maybe she's not a JW and that seems to be all that matters to you.
I am not judging her, merely telling you from the other side of the story to explain why some act like the victim when they were actually the perpetrators....responsible for their own behavior and the consequences that follow.
As I mentioned, I have had a few members of my own family disfellowshipped for serious breaches of God's law, and all but one has returned, chastened and grateful to be "home".....like the prodigal son. That parable is not there for no reason. If the father in the parable represents God and the sons are those who are dedicated to him, the younger son decided that he would take his inheritance and go and live the way he wanted to. The Father did not stop him, but let him go without any further contact. It wasn't until the son hit rock bottom that he realized that the world and false friends are not what he thought they would be....so he felt regret about his actions and in dire circumstances, he decided to return home to his father.....but how did he return? What attitude did he display? Were there demands about how things should be if he came back? Was he in a position to dictate the terms? Or was his return with a contrite heart, feeling unworthy of receiving his father's forgiveness?
That is what our heavenly Father looks for in his erring children. Discipline is done out of love as Paul said...
Hebrews 12:5-6....
"And you have entirely forgotten the exhortation that addresses you as sons: “My son, do not belittle the discipline from Jehovah, nor give up when you are corrected by him; 6 for those whom Jehovah loves he disciplines, in fact, he scourges everyone whom he receives as a son.”
Those who think that God does not approve of warranted discipline are dead wrong about that.
Solomon wrote...
"Because sentence against a bad deed has not been executed speedily, the heart of men becomes emboldened to do bad."
We don't discipline our own children because we hate them.
If the girl's mother knew Jehovah, was dedicated as a disciple of Christ, but committed immorality with an unbeliever anyway, can she be surprised by the discipline? Did she not know better? Was there an excuse?
Did the mother keep knowledge from her daughter in telling one side of the story that led to her birth?
As I said, no one is disfellowshipped unless there are valid scriptural grounds. We don’t know the circumstances, but even committing immorality will not result in disfellowshipping if there was genuine repentance....God is all about forgiveness, but our conduct is also about the exercise of free will....and copping it on the chin when we are disciplined.
God does not force us to comply with his laws, but we understand that there are penalties if we don't. That is the way the world operates...is it not?
We don’t know what story her daughter was told, but it’s human nature to minimize what we do wrong, and to exaggerate what the other person did to paint ourselves in a better light. At the end of the day, Jehovah knows....so no one gets away with anything.