My son recently married his girlfriend of 4 years. She came to the US from Trinidad at the age of 3 with her father who has a green card. He never applied for anything for her. She has no ss# or itin#. She attended 12 years of public school in NYC and graduated in June. My son is an American citizen. My daughter in law recently filed taxes for a job she had while in HS. She also filed documents with her 1040 to receive an itin #. What is her legal status in the US?

Not enough information. If her father truly never filed anything for her at the same time he got his PR, then she has no lawful status.

If she entered lawfully, and as a minor child, it is likely she did, then her husband can file the relative petition for her as she is eligible for AOS under section 245(a). She will need to prove up her lawful entry. If she doesn't have her I-94, find an attorney to assist. The unlawful presence and unauthorized employment is waived with no penalty fee. He should file immediately. You can confirm all this with an experienced immigration attorney. Congratulations and good luck.