The camera shot makes it look like she’s headed it onto his own arm!
But this for me is one of those that’s never going to be overturned, whatever the on field call was. Three defenders challenging for the ball, Maguire inadvertently being struck on the arm by the ball after being jostled and bumped by his team mates. Referee says penalty, it stands. Referee says no, call stands.
Disingenuous comparisons elsewhere with the Antonio and Ndidi penalties going around too - both are clear blocks with the hand or the arm. This ball is dropping and he’s making a legitimate attempt to play the ball fairly. I can understand the doubt in this situation.