Is there a process for an illegal immigrant who has married a US citizen to acquire citizenship?

I do not know of any process for an illegal immigrant who marries a US citizen to go directly to US citizenship. The first process would be to obtain permanent residence. If your friend entered the US legally, she is probably able to adjust her status to permanent residence with U.S.C.I.S. If not, she may still be able to obtain such through a much more convoluted method, the I-601A provisional waiver which involves an I-130 relative petition, I- 601A provisional waiver application which is adjudicated in the US while she waits here, and if approved, consular processing in the home country with the American consulate or embassy. The I-601A provisional waiver began processing in 2013 and is a very good device to gain permanent residence, but is not one of the easier applications.Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.