Diddy's girlfriend needed a little sun before a little bubbly for New Year's -- and she definitely got it ... on all sides.
Paps got Cassie hitting the beach in Miami hours before her guy threw a blowout of a NYE party at their house -- where Diddy ended up helping a drunk woman who'd passed out.
As for Cassie, looks like she was gettin' her sip on before the clock struck 12. She was all smiles too, and why wouldn't she be? It's easy to be happy when you look this good.