Julia Roberts‘ subtle and strategic nips and tucks are giving Jennifer Aniston a serious case of sour grapes, an insider exclusively tells Life & Style.

Roberts, 56, “is quietly boasting she’s found a way to turn back the clock without going over the top,” the source says. “She looks fantastic. You can see that she’s had a little work on her eyes, but nothing too extreme. It’s done wonders for her self-esteem and her marriage because her husband, Danny Moder, can’t keep his hands off her.”

But Roberts’ youthful glow is causing Aniston, 55, to turn green with envy, according to Life & Style sources.

“Jen’s getting trolled for the work she’s had done, while Julia is being feted as this forever young sex symbol. She is frantically trying to find out who Julia’s doctor is, but she’s getting shut out,” says an insider.

“It looks like Julia’s had Botox to her lower to the forehead and her upper eyes done,” says top Chicago plastic surgeon Dr. Otto Placik. “I think she’s likely had Botox and filler to the lip region and maybe in the cheeks as well.”

He also points out some plastic-surgery fails on the former Friends star. “I think Jennifer got filler eyelids that is not sitting well, and it looks as though her lower eyelids have been tightened,” says Placik, who has not treated either star.

“It looks like she’s got undesirable filler in what we call the tear trough. And then she looks like she’s definitely had some filler to her lower lip.”