She wrote: "Momma, Brian, and me are all so grateful for all your well wishes. My lil sissy Gracie Elliot Teefey was born on June 12th. Luv you all XO."
Mandy divorced Selena's father, Ricardo Gomez, when the Love You Like A Love Song singer was five-years-old, before marrying Brian Teefey in 2006.
Demi Lovato was quick to "congratulate" her life-long friend on becoming a "big sister" when she made the comment on her own Twitter account today.
She tweeted: "@selenagomez IS A BIG SISTER!!!!!! Everyone congratulate her and her family!!!!!! #CONGRATSSELENA!!!!"
Speaking before Gracie's birth, Selena admitted she would "spoil the baby" and wanted to be "more like a cool aunt" in the future.
She previously said: "I want to be the best sister in the world. I'm really going to spoil the baby! I can't wait ... There's going to be a big age difference, so I think I'm going to be more like a cool aunt
Living the good life as they continue their break from the chaotic world of superstardom, Justin Bieber and Selena Gomez have been enjoying Maui, Hawaii.
Wo can blame Justin for crushing on Sel, she looked sexy in a pink bikini as she lovingly held hands with her boyfriend, who sported a pair of swim trunks as he strolled the shoreline with his lady.
Justin recently Tweeted , "sunshine...aint complaining"
Bieber also showed off his new tattoos, as his body is now adorned by two tattoos - one being a small bird on his waist while the other is a vertical Hebrew inscription down his side which reads, “Yeshua,” meaning Jesus.
A few days ago we saw them holding hands, but these new photos in the water are a whole lot more steamy! Wow!
sel and justin
Selena Gomez is a great actor. I really love her singing also. Wizards of Waverley place has been a hit. Her evil schemes are great in the show. She loves her family but she always annoys her brother Justin and plays tricks on him. I just love her show and if you do to just comment and say yes.Selena Gomez is a great singer as I said I love her music because they just touch my heart and I always watch her show. Selena is comical person who makes everyone laugh. She is a inspiration to kids with her acting and I hope she can make more shows so I can be inspired and more people can be inspired. This was a great opportunity for me to share my feelings about Selena and I hope everyone else likes them because I put my heart and my mind to say these things.
Selena Gomez says she is eager to record an entire album in Spanish. The Disney singer, who has Mexican roots, reveals she is hoping to master the language soon. She already recorded a Spanish-language version of her hit single, "A Year Without Rain. "It was awesome!" Selena said when asked about the song. "I actually want to record an entire album in Spanish. As soon as I have time, I'll do it." She added, "I really want to get Rosetta Stone, because I really need to learn my language,. "I practice [Spanish], but I can understand it better than I can speak it."
The US pop star is a big fan of the 'Promise This' singer and insists it would be a dream come true if they could record a song together. She said: I'm so a massive fan of Cheryl. I want to be her best friend! I love everything about her. She's my role model. It would be my dream to collaborate with her."
As well as wanting to work with Cheryl, Selena, 18, is also a fan of Katy Perry, and has revealed she was so grateful when the 'California Gurls' hitmaker let her record the song 'Rock God' instead of her.
She told Top of the Pops magazine: "Everyone wants songs written by Katy Perry. I asked her and she was so nice - she just said, 'Yeah, you can have it.' She was very kind."
The song 'Rock God' appears on Selena's second album 'A Year Without Rain'.
Selena Gomez says she is taking inspiration from her fans for her clothing line.
"Inspiration for my clothing line is mainly my fans. I love clothes and I love fashion. I think it's a wonderful way of expressing yourself," she said.
"I basically wanted to create a line that was very personal to me and something I think my fans would like. Hopefully, they will enjoy it when it comes out."
The clothing line will be available in Fall 2010.
She has also said, "I want the pieces that can be easy to dress up or down, and the fabrics being eco-friendly and organic are super important."
"Inspiration for my clothing line is mainly my fans. I love clothes and I love fashion. I think it's a wonderful way of expressing yourself," she said.
"I basically wanted to create a line that was very personal to me and something I think my fans would like. Hopefully, they will enjoy it when it comes out."
The clothing line will be available in Fall 2010.
She has also said, "I want the pieces that can be easy to dress up or down, and the fabrics being eco-friendly and organic are super important."
