Olivia Culpo wasn't lyin' when she said she was keeping Danny Amendola's birthday present ... rockin' her ex's $12,000 Rolex and a bad ass leather outfit in Miami!!
The gorgeous model shaded the Dolphins star on social media after he was spotted flirting with a sports reporter on the beach last month ... saying she was gonna keep the flashy watch for herself.
Not only was O.C. sporting her ex boo's ex-birthday present ... she was wearing skin-tight leather pants that would make Olivia Newton-John's Grease character jealous ... along with a black hoodie, leather jacket and black beanie.