I agree with Star. If Piglet tried her hardest but the other team was better or she just couldn't get the puck out of the goal (for some reason, I'm assuming she was the goalie) or whatever, well, those things happen. If she "bombed" because she wasn't in the game zone, well that happens, too. My daughter played field hockey in HS, as a goalie. Sometimes, she blocked the shots, sometimes, she didn't. One game she totally bombed, couldn't block a goal for her life. She got her period two days later and realized that she had not been at her best at that time.
Maybe you can sit down with Piglet and ask her how she feels about the game overall. Have her analyze everything, not just her role. I am sorry, but I don't believe that in a team sport, ONE person makes or breaks the game. Is it fair to blame Derek Jeter if the Yankees lose just because he had no hits, was tagged out on a walk and hit the catcher with the ball the one time he caught it if the other players did not play well either? Sometimes, the other team just has a better day. Maybe if Piglet can look at it in the wider scheme, she might be more willing to acknowledge (admit is tough for a 13 year old) she had a bad day.
In my opinion, team sports are wildly over-rated. I never played on a team and neither did my H. The only one of my 5 kids who played a sport after elementary school was my only daughter (unless you count chess team, which difficult child and PC14 are on) and she did it because her friends were doing it and for the exercise. The win at all costs attitude I see in sports on a too regular basis is very offensive (and I'm a trial attorney by profession so I am not a non-competitive person by nature, just no a physically competitive person).
In any event, good luck to Piglet, I hope she can turn this into a learning experience.