Ashlee Simpson Showcases Skinny Bikini Body on Vacation in Mexico

Credit: FameFlynet

Ashlee Simpson is going to become a second-time aunt very, very soon -- but in the meantime, Jessica Simpson's little sister is squeezing in some pool time south of the border! Vacationing with pals in Cabo San Lucas, Mexico, the "Bat for a Heart" singer, 28, displayed her skinny physique in a colorful bikini Saturday June 22. The single, divorced mom to son Bronx Wentz, 4, accessorized with a floppy hat, oversized sunglasses and black, sheer coverup.

Back in April, Simpson's ex-husband Pete Wentz praised her skills as a mom. "I feel like we both realize that we're parents and we're in it for our kid. That's made it really easy," Wentz told Andy Cohen on Watch What Happens Live. "I feel like, as a mom, she's awesome. She's an awesome mom and we get along really well when it comes to our kid now." (The pair called it quits in 2011.)

Ashlee's big sister Jessica, meanwhile, is in the final stretch of her second pregnancy, and was spotted grabbing lunch the same day in Santa Monica, Calif. with fiance Eric Johnson; the engaged couple will soon welcome a baby boy to join daughter Maxwell, 13 months.