Abramson is full of shit. She did not "let third parties into a criminal case." They are not parties. They are amici curiae, and yes, those are allowed to brief, and sometimes argue, in ALL KINDS OF CASES, INCLUDING CRIMINAL CASES - there is an actual ABA article on this from a few years ago (as in, pre-dating this case) noting that yes, amici curiae appear in criminal cases, including in trial courts. And the family relationship of a lawyer to another lawyer is also not something courts take into account absent other circumstances - it's not a conflict of interest, per se.
Not excusing Cannon at all here - I think the fix is in, and I think she'll fuck this up. But Abramson is flat-out wrong, and it does us all a fucking disservice when dissenting voices are so fucking wrong that I can only conclude they're being purposefully dishonest.