At a minimum your gf is more than likely eligible for unemployment compensation since she did not violate a clearly articulated and written rule. She may want to request her personnel file and make sure she has the most up-to-date handbook.
Check with a local employment attorney who will be more familiar with NY employment laws.
Unfortunately, there is no law to protect an employee from getting fired for attending a family funeral. But I do not think they would want to be known as a company that does that. Instead of a lawyer, have her get a letter from a clergy member asking for consideration to take her back, and send it to Human Resources. A smart PR campaign might just get them to reconsider.