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Demi Lovato is officially 20 years old, and her celebrity friends have taken to Twitter to wish her a happy birthday!

We're most excited about her flirting partner Niall Horan from One Direction wishing her a happy birthday -- there is definitely something going on here!

Happy Birthday Demi from The Hot Hits!

Niall tweeted, "@ddlovato happy birthday honey! Have a lovely day! See ya soon"

HONEY. SEE YA SOON. Just date already!

Of course Niall wasn't the only famous person to wish Demi a happy birthday. Plenty of other stars also sent her their love!

Kim Kardashian tweeted, "Happy 20th Birthday DemDem!!!! I love you @ddlovato"

Her sister Khloe wrote, "Happy Birthday @ddlovato!!!!!! May glitter rain all around you today! Shine on baby doll!!!! Muah!!!"

Fellow Disney star Miley Cyrus said, "@ddlovato happy birthday I'm sending you lots if x's not wasting time on o's =] have the best day everrrr xxxx"

Travis Clark from We The Kings tweeted, "Happy birthday to the beautiful and talented @ddlovato :) I miss your face haha <3"

Simon Cowell wrote, "Happy Birthday Brat (@ddlovato) lots of love. Simon"

Demi's Sonny With A Chance co-star Tiffany Thornton tweeted, "Wishing @ddlovato the happiest of birthdays :) love you!!"

No birthday message yet from BFF Selena Gomez...