Does the petitioner for the I-130 have to be the one to file an affidavit or can someone else sponsor me?

The I-130 petitioner (your mother) must file a Form I-864 Affidavit of Support for the beneficiary (you). If the petitioner does not have sufficient documentable income, it may be necessary to have a joint sponsor who also files an Affidavit of Support. The joint sponsor generally may be any U.S. citizen or Permanent Resident who has sufficient documentable income and who is willing to assume the responsibilities specified in the Affidavit of Support. If your mother filed the Form I-130 petition without an Affidavit of Support, then it appears that she is not thoroughly familiar with the requirements for the application process. It would be wise for you and your mother to work with an immigration attorney who can assure that the process is properly handled in order to avoid further delays and even more harsh consequences. Some immigration law firms, including mine, offer legal services on a "flat fee" basis so that a client will know the total expense from the very beginning, and a few immigration law firms, including mine, offer an initial consultation free of charge.