I saw that footage too. Easily explained. Some mail in ballots were torn, or damaged so they wouldn't go through the counting machine. (Thank you, Louis DeJoy.) What the woman in question was doing was, under the watch of observers of BOTH PARTIES, marking clean, fresh ballots to ensure those VALID AND LEGAL votes were counted properly. Simply that. Period. No irregularity about it at all.
CNN didn't decide the winner. The American electorate did. All CNN, MSNBC, all the major networks (including FOX, btw) was report and confirm what the voters did. Trump can (and has) challenged things, but none of his challenges so far have any merit whatsoever. None. Nichts. Nada. Rien. NOTHING. Trump can complain all he wants, but unless his complaints have any firm evidence behind them (and so far that has not been the case) it's just much sound, fury and whining, signifying NOTHING.