How can I factory reset my Android Mini 7100 Phone?
I think the easiest (and non-sketchiest) solution for this will be to help your sister recover her Gmail password. Once you have that, you can use the Android Device Manager to reset the phone password, or erase the phone memory from the computer.


This is the only solution I will post here because resetting an android without access to a gmail account is often done with less-than-ideal intentions.