(CNN) Lori Loughlin's daughter Bella Giannulli broke her social media silence to wish her mother a happy birthday.

Loughlin turned 55 on Sunday and has been keeping a low profile ever since she and her fashion designer husband Mossimo Giannulli were among dozens of wealthy parents charged in a college admissions cheating scheme.

Prosecutors allege that the couple paid $500,000 to a fake charity to get their two daughters, Isabella, 20 and Olivia Jade, 19, into the University of Southern California by falsely designating them as crew team recruits.

Loughlin and Giannulli have pleaded not guilty to charges of conspiracy to commit fraud and conspiracy to commit money laundering. Each charge is punishable by up to 20 years in prison.

On Sunday their daughter Isabella posted a black and white photo with her mother on her official Instagram account.