10/02/2006 at 01:00 AM EDT
By the time Kate Bosworth
turned up at New York City's Fashion Week, she admittedly had been having a rough few weeks. First came her breakup with longtime boyfriend Orlando Bloom
. Then came what she thought was an attack of allergies, but "I think it turned into a little sickness," Bosworth said while sitting in the front row of the Sept. 14 Zac Posen show.
Still, it was Bosworth's physical appearance that most concerned friends and onlookers as she made the runway-show rounds and stopped in at the afterparties. "She's so small, it's frightening," says one insider who saw her at Fashion Week. Adds another attendee and well-placed Bosworth source: "She's always been small, but now she is really, really skinny."
One possible reason: With her recent split, "she's emotionally and physically strained," says the source. And although the 23-year-old actress's rep declined to comment on her weight, Bosworth has spoken in the past about pressure to be thin. "I think part of being an actress [is] that your body's your tool," she told Showbiz Tonight
in July. But since Bosworth hasn't filmed anything in over a year now, some are hoping she will take a closer look at herself. "Every time I saw her," says the source, "I kept thinking, 'Please eat something.'"
"A size zero is big on her," says one source of Bosworth (at the Sept. 14 Zac Posen show).
Bosworth added about 20 lbs. of muscle to play a surfer in 2002's Blue Crush