She should file using the I-130 Receipt notice. I-864 is filled-out by your brother, and the rest of the forms by your mother. In general, send the following four packets (*note that I-765 and I-131 packets are optional, but highly recommended) in the same envelope to the Chicago Lockbox: I-485 with I-130 Receipt notice, I-864 and supporting documents, electronic I-94 copy, filing fees, etc.; I-765 with electronic I-94 copy, etc.; and I-131 with electronic I-94 copy