Christopher Schwarzenegger and Maria Shriver
Cindy Gold, The Women's Conference
07/25/2011 at 03:00 PM EDT
After a week's stay in the hospital for internal injuries suffered during a boogie boarding accident
, 13-year-old Christopher Schwarzenegger is improving and is expected to be released by mid-week, a family source tells PEOPLE.
Maria Shriver has kept vigil at her youngest son's bedside since he was admitted to an L.A. hospital
with a collapsed lung, broken bones and broken ribs on July 17.
"She was shaken horribly," says a source close to Shriver, who was with Christopher on the Malibu beach when he got caught in a powerful wave.
"This is her baby," the source says. "She has been at the hospital nonstop, 24-7. She is sleeping there. How much can she take right now?"
The beach accident is just the latest personal set-back for California's former first lady, who filed for divorce
from Arnold Schwarzenegger two months after the actor's public admission that he fathered a child
with the couple's longtime housekeeper.
But Shriver, say friends, remains resilient.
"It's very hard on Maria but her friends and family are there with their love and support," says another source, who notes her other children have helped Shriver through this latest crisis. "All the kids are visiting – they all adore and love each other and they are all there for each other."
Also paying regular visits to Christopher at the hospital: Shriver's estranged husband.
"Arnold is a great father," says a source close to the family, "and he and Maria will always come together when it comes to supporting and loving their children."
Reporting by LORENZO BENET