Please refer to parents sticky thread (1st page) in Family based forum for detailed information on consular processing.
In short, after I130 approval, I130s will be transferred to NVC. After that they will send I864 fee bill and DS3032 to petitioner and separately DS3032 to beneficiary.
Submission of DS3032 would trigger IV fee bill which in turn triggers DS 230 Part I going to the agent. (This is for standard review consulate, procedures are somewhat different for Application review consulate).
Upon payment of I864 fees, petitioner will receive I864.
Once your I864 and DS 230 Part 1 are with NVC, they review them and if they are complete, they will forward the entire file to the consulate and notify the agent. Next your mother will hear from the consulate when their interview is scheduled.