If she does not have tax returns because she did not work previously, that's ok but she still needs to file an I-864 form. She should also submit an employer letter and/or pay stubs if available.
Attorney Jennifer Ahn's answer is to provide general information only, and should not be construed as legal advice on any subject matter. The content of this answer is not intended to substitute accurate legal advice, which is relevant to all the facts and circumstances of your specific case. This answer does not create an Attorney-Client relationship. (847) 297-9200
Since she is petitioning you, she must complete form I-864.
Mr. Shusterman's (former INS Trial Attorney, 1976-82) response to your question is general in nature, as not all the facts are known to him. You should retain an attorney experienced in immigration law to review all the facts in your case in order to receive advice specific to your case. Mr. Shusterman's statement above does not create an attorney/client relationship.