One, why haven't you reported your aunt for voter fraud? Voter fraud is a very serious issue and it seems to me that you're letting a criminal go free. This can be easily verified by telling the government and having the three others confirm who they voted for.

For two, if she is mailing in the ballots, then is she forging their signature as well as collecting their SSNs? Or are they simply signing on the ballots themselves agreeing to the votes? In which case is that truly fraud or not? If she's forging signatures then she's also committing identity theft which is a very serious issue, one that I hope you agree deserves reporting.