"The club has to be able to rely on its own resources," Berlusconi, daughter of club president Silvio Berlusconi, told French newspaper L'Equipe.
Milan, once bankrolled by former Italian prime minister Berlusconi, upset fans with an austerity drive that led to them selling frontman Zlatan Ibrahimovic and centre back Thiago Silva to Paris St Germain for 62 million euros in the off-season.
Barbara Berlusconi said cutting costs was the only way forward for the Serie A club.
"I understand (the fans) but we have to explain to them that we have followed the only possible path," she said.
"We have grown up thanks to an excellent business model - a passionate sponsor pouring money into the club - which does not fit today's situation," she said.
"Soccer has kept on developing but it has lived on credit. We have seen recently at national level what excessive debt can lead to."
Milan, seven times European champions, began the season in poor form but have recovered some ground in recent weeks, rising to seventh in the league after three successive wins and qualifying for the knockout stages of the Champions League.
Berlusconi said Milan could nurture their own great players, such as Italy international Stephan El Shaarawy, rather than buy them in.
"We can raise great champions at home. We let Ibrahimovic go but we have found El Shaarawy, a gifted young player," she added.
"When I talk about a home-made champion, it doesn't only mean he comes from our youth academy. El Shaarawy doesn't, but we bought him when he was quite young and we've helped him mature. We have the experience to allow his talent to blossom.
"When a champion leaves, we just grow another," she added.
El Shaarawy is the league's top scorer, with 13 goals in 16 appearances.
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- Zlatan Ibrahimovic