Arsenal and Napoli are reportedly keen to sign the Italy striker, who joined Milan from Manchester City in January 2013.
Balotelli came in for criticism during Milan's disappointing 2013-14 campaign - when the team finished eighth - and Berlusconi offered no assurances that he will remain at the club.
She told the club's official website: "Balotelli is a great player. But the way I see it, I don't believe that someone can be irreplaceable.
"We will see what happens."
Berlusconi assured Milan fans that the club have the finances to back new coach Filippo Inzaghi as they strive to get back on track next season.
She said: "Milan is a very solid club, we are positioned very well in turnover and are calm for the upcoming seasons. My father wants to continue investing in Milan."
