Le Sommer held her nerve to dispatch the spot-kick in the 72nd minute, giving the host nation a 2-1 victory.
An upset was nearly on the cards when French center-back Wendie Renard - who kicked off the tournament last Friday with a brace - scored an unfortunate own goal. That canceled out teammate Valerie Gauvin's opener 43 seconds into the second half and gave Norway hope of leapfrogging France in the standings.
But the advantage was soon restored. Referee Bibiana Steinhaus awarded a penalty after Norwegian midfielder Ingrid Engen's follow-through caught Marion Torrent in the leg. Steinhaus consulted with the video assistant referee (VAR) and later reviewed the images herself before making the decision.
France is perfect in the tournament with six points out of six. Despite Wednesday's bitter defeat, Norway remains in second place with three points, ahead of Nigeria on goal difference.