1. It's advisable to obtain divorce from an Indian Court, as US is not considered as a reciprocating country by Indian Government.
2. If it's possible, let her convince her husband to agree for Mutual Consent Divorce, which saves time and money and all the differences can be resolved mutually such as custody of her daughter, division of assets, alimony/maintenance, etc., She can get alimony which inturn depends on her earning potential, educational qualification, duration of marriage, etc. Her daughter will be entitled to a share in the ancestral property.
3. Her daughter, as a coparcener, is entitled to a share in the ancestral property, which can be resolved during your niece's divorce proceedings.
4. Your niece can find the details of her husband's properties in India by applying for Encumbrance Certificate in the jurisdictional Sub Registrar's Office where the property is located and also from her known sources, such as through friends and relatives.