What if the infraction happened on Sunday, Lexi had "won" by one stroke, and the viewer sent in the email on Monday. Would you take away the trophy, tell the 2nd place golfer that she had won? If there was a tie for 2nd have a play off starting as soon as the competitors could get back to the course?
When the round is over it is over. Once the scorecard is accepted it is the score. If after the fact you find blatant cheating, take away the victory but don't rely on TV viewers to find incidental infractions of the rules.
SoCal