It did start that way, though.
The two grew up with each other -- first meeting on the set of "Barney & Friends" and then emerging as Disney Channel stars. Now that they have their own respective careers, their friendship is stronger than ever. But there were a few years in between when fans questioned whether they were still pals.
In light of their recent reconciliation, let's take a look at the friendship of Demi and Selena:
'Barney & Friends'
Selena and Demi met as kid actors on the set of "Barney & Friends." They were both 7 years old and most of their scenes as Giana and Angela were booked together.
You can really tell that they were BFFs during their vlogs in 2008. Here, you get a glimpse at their silly handshake.
2008 Teen Choice Awards
Delena -- that's their ship name -- looked super adorable at the 2008 Teen Choice Awards.
'Princess Protection Program'
Sel and Demi filmed this Disney Channel movie together in Puerto Rico. Released in 2009, it's the first time since 'Barney' since they worked together.
'One And The Same'
To promote "Princess Protection Program," the ladies recorded the BFF anthem "One And The Same."
They do everything together.
In 2009, they had a joint spread in People where they said that they do everything together.
When a London fan asked Demi, "How's Selena?" in 2010, she said, "Ask Taylor." Selena had been hanging out with Taylor Swift, and it seemed like Demi was jealous.
'We're both busy.'
In May 2010's issue of Girl's Life, “We’re both busy, and I wish the best for her. True friends don’t let their friends or family be mean to you. If you can’t trust somebody, you can’t be friends with them.”
Demi checked into rehab in 2010, and a few years later she gave an interview revealing the friends who were most supportive while she was healing: “Nick especially — he’s always been there for me. And Selena because she called me crying when I was in there and was just so worried,” Demi said. “I was like, ‘Look, I should be the one crying, it’s all good!’ But she was so worried and ever since then we’ve gotten closer.”
2011 Kids' Choice Awards
When Demi got out of rehab in 2011, the two friends reunited at the Kids' Choice Awards, laughing hysterically on the red carpet.
As a pre-show co-host in 2011, Selena interviewed Demi on the red carpet. They didn't say too much -- besides chatting about their love for Missy Elliott.
2012 Teen Choice Awards
Demi and Selena both attended the Teen Choice Awards in 2012, but didn't talk or pose for pictures, and fans caught on. At the end of the night, Selena left to go to a birthday party boyfriend Justin Bieber threw for her, but Demi went her own way.
Showing love for their songs
"Heart Attack" and "Come and Get It" both came out around the same time in 2013, and the singers tweeted their appreciation for each other's tracks.
In May 2013, Demi stopped by our offices for "Live From MTV." She dished on Selena, saying that they don't necessarily have to talk every day to be friends and that she still wants to have her in her life.
“We’ve been through a lot together, we’ve had periods of times we here we grew apart and we just didn’t really talk,” Demi said. “Now we are in a place where I think we realized that life is so short and that when you have people in your life that love you so much then, you should just always be around them. She’s going to be a big sister, and I want to be around for that. Everything about her, she has a great soul, she’s talented, she’s beautiful, and she will always be really, really close to my heart.”
'The evidence of forever'
In November of 2013, Selena performed on "The X Factor," while Demi was a judge on the show. They took an adorable snap backstage, which Sel captioned, "It's just the evidence of forever. No matter what ddlovato."
Out to dinner
Delena were spotted out to dinner in January 2014 in Craig's in West Hollywood. Looks like everything's going well?
Fans noticed that Demi unfollowed Selena on Twitter and Instagram in July of 2014. She also reportedly posted and quickly deleted this tweet that said, "Swimming away from your bullsh-- by bitch."
'People grow apart'
“I think it’s just one of those things where people change and people grow apart,” Demi said when Andy Cohen asked her about why she unfollowed Selena in August 2014.
In August 2015, fans noticed that Demi re-followed Selena. Good news!
On Demi's birthday, Selena tweeted at her, writing, "IM so grateful you were born." Demi reciprocated the love, saying, "I'm so glad you were born too... :P #forever #nomatterwhat."
'Cool For The Summer'
Selena and Taylor Swift could be seen dancing to Demi's performance at the 2015 VMAs, although mostly Selena was quietly watching.
'Same Old Love'
In September, Demi posted a silly selfie of them making a weird face, writing, "Look at how #coolforthesummer we are.. Friends for years, #sameoldlove." Again, we're left cheering for the two friends. Friends forever!