The singer and actress – who is engaged to former NFL star Eric Johnson – is pregnant with the couple's first child and was thrilled when doctors revealed she is having a daughter.
A source told In Touch Weekly magazine: "She's telling people it's like winning the lottery, twice. Jessica really wanted to find out the baby's sex, she hates surprises. She and Eric are both so happy."
The couple – who are set to wed next month in Hawaii – are currently painting the baby's nursery pink and friends claim they are already considering the names Morgan and Karen. Jessica - who was previously married to singer Nick Lachey - has made no secret of her desire to become a mother and recently admitted she couldn't wait to have kids with Eric.
She revealed: "I definitely see myself having a family with Eric, so that's exciting to think about."The news of a granddaughter will also please Jessica's mother Tina as she recently revealed she would like more grandchildren to go with two-year-old Bronx, the son of her other daughter Ashlee Simpson and estranged husband Pete Wentz.
She said: "Obviously I'm looking forward to having more grandkids. Bronx is the love of my life. I don't mind boys or girls, I'll take anything I get. I'm not picky!"