Legal Question in Family Law in Pennsylvania

You don't mention how old she is now. Depending on her age, have you tried facebook? twitter? linked in? How about one of the people finder services, like www.zabasearch.com? Does she have a unique last name? That will make the search easier than if her name is something like Jane Smith.

What about hiring a private detective or missing heir service? It will cost more, but it is very difficult for people to remain totally anonymous.

If your niece was adopted and had her name changed, it will be more problematic as it will depend n the adoption laws of the state where the adoption was filed. Most states seal the records. Some organizations will act as intermediaries and contact the adoptee on your behalf and if your niece wishes to have contact then the intermediary will arrange for a sharing of contact information.

Even if your niece was adopted, I would still try facebook or a similar site to see what turns up. Your niece might also be searching for her biological family or relatives so if you put information out there she may see it.