And yet......no one is arguing that she made an "illegal lane change", outside of the officer. The issue is that she ran thru a stop sign which prompted the stop in the 1st place. THAT'S what she was wrong about in the 1st place.
Again, just speculation here, but the reason he was citing her for the illegal lane change vs the more egegious, and likely more costly, running a stop sign citation, is that it was a lesser offense. Again, just speculation, but the stop was perfectly legal