Her friend asked her to pray for her to have a baby girl
Question

One day one of the sisters, who was pregnant, asked me to pray for her that she be blessed with a daughter. Is it permissible to offer such a supplication?
Praise be to Allah.What is best is for a person to ask his Lord for righteous offspring, because he does not know whether a daughter or a son would be better. Hence one of the supplications of the slaves of the Most Gracious is (interpretation of the meaning):
{And those who say, “Our Lord, grant us from among our wives and offspring those who will be a source of joy for us, and make us an example for the righteous”} [al-Furqan 25:74].
But if the mother longs for a son or a daughter, and asks her Lord for that, then she should accompany her supplication with a prayer that the child be righteous and guided, such as saying: O Allah, I ask You for a believing, righteous daughter who will be a source of joy for me, and the like.
There is nothing wrong with you offering supplication for her and saying: O Allah, bless her with a righteous daughter who will help her to obey You and seek Your good pleasure, and so on.
And Allah knows best.