LeAnn Rimes is celebrating her friend's birthday with two of her favorite things: Twitter & bikinis!

The country singer, who turns 31 herself later this month, took a trip to Cabo San Lucas this week for her buddy Lizzy's 40th birthday -- and she's been tweeting up a storm since being there.

With bikini pics on Twitter and videos of her dancing around in a two-piece and serenading the b-day girl on Vine, it's almost like we're there with her!

"Girls girls girls..... Happy 40th to the hot chick in the middle!!! Love you Lizzy," she posted along with the photo above.

And be sure to check out the Vine video of her below:

LeAnn's bod has been looking great these days, don' you think? See how her beach physique has changed through the years in the gallery above!

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