I don't make mine practise . She did G2 in year 6 and will be doing G4 this summer (Y8). I haven't pushed it and she chooses to practise when she wants to, which is 3 or 4 times a week usually. She's keeping up with the other girl in her lesson though so i assume the other girl doesn't practise either she's doing ok.
I would think the tiredness and telling off are the real reason for the tears, they would be for my dd.
My DD1 (15) found it a big on piano. Needed a year between G2 & G3, and it's not her first instrument. But a friend of hers a couple of years younger is going straight from G2 o G4 (also not first instrument).