Manchester United legend Gary Neville has branded Balotelli an "embarrassment".
But Cristina said that people in England are too quick to criticise an Italian player when they aren't performing at their peak and that her brother is simply missing his family back in Brescia.
"Mario might have not been brilliant, but putting all the blame on him for the defeat is totally unfair," she said.
"He said, 'I miss my family and friends but I think this experience in England will help me grow as an individual'."
Cristina is angriest at the media for portraying her brother in a negative light. There are numerous stories she claims are untrue - saying he never bought a Harley Davidson motorbike in breach of club rules and a dead fish was not found on his Maserati, which one paper said was apparently a sign the supporters dislike him.
"Supporters love Mario," she said. "Every time I go to see a football match in which he plays I find myself randomly in groups of supporters who sing the Balotelli song: 'Oooh Balotelli... he's a striker...'
"I always tell him. I think they like him because he's fun and genuine like them."