In my opinion........

How do you know they said it harshly? I think part of their responsibility is to be honest and set realistic expectations (in an encouraging and helpful way), and10 isn't very little. Not everyone is good enough right now and some may never be. And she lost an election? Sounds like the same issue. What age is old enough to learn that you sometimes have to go home and get better at a craft?

I hated public schools in the US, but it sounds like you want them to let everyone win at everything they want. I expect her to hate that because she is a child. But how exactly is she going to make it in the world if she becomes an adult thinking she's going to win every election and position she wants?

I think it would be a much greater disservice to set the bar at the floor to avoid hurt feelings. Of course, they should set expectations in an encouraging way, but that in itself is a valuable lesson. Not everyone is going to be encouraging. Few are. It's ultimately on her parents to teach her the value of keeping at her goals.