The phrase "___ has had work done" means that a person has gotten cosmetic surgery. Cosmetic surgery is a kind of surgery that a person gets to make themself look better. Some examples of cosmetic surgery include:

• a face lift (reducing wrinkles in the face by pulling the skin tighter
• liposuction (getting fat removed)
• a "boob job" (breast enlargement)

You can gossip about someone's cosmetic surgery by saying that they've "had work done" or just "had work":

Do you think she's had work done?

Look at his face. He's definitely had work.

This phrase is a little rude, though, so you usually wouldn't use it when talking directly to the person who got cosmetic surgery.