Modelling the right behaviour is obviously a good suggestion, but I’d also talk to her about it.
Not in the immediate aftermath, when she’s still frustrated and unable to take anything in, but later when she’s cooled off.
I have two tennis players and when they were first starting out, albeit younger than 7, they (well, one more than the other), would demonstrate some of these behaviours.
So later, we’d chat about it. Ask a few questions.
‘Looking back, what do you think about your reaction to the outcome of that match?’
‘What do you think people watching might have thought?’
’If you’d won that game, and your opponent had reacted the way you did, what would you think of them?’
Get them to think about it. It’s conversational, and it’s not telling them off. It gets them thinking.
And then talk. It’s OK, in fact, it’s really normal to feel disappointed after a loss. But you’re not always going to win. Nobody always wins. Not even the best players in the world. So you need to think ahead about how you will react IF you lose, so that you don’t embarrass yourself. Being a gracious loser shows real strength of character and impresses people’…. yada, yada…
We found conversations like this really helpful, and the behaviour was soon knocked (metaphorically) out of them because they could understand themselves why it wasn’t a good look.