
How/when did they meet?
They likely met in 2006-2007, according to an interview Selena did in 2019.
Taylor's first lead single "Tim McGraw" was released in summer of 2006 and Wizards of Waverly Place began airing on Disney Channel in 2007.
In a separate interview in 2017 with KIIS FM UK, Gomez said "We actually dated the Jonas Brothers together! It was hysterical," Gomez told the hosts, referring to her relationship with Nick and Swift's with Joe.
"It was amazing, because she was the girl with the big curly hair and all the bracelets and the cowboy boots. And I was definitely up-and-coming, and we just clicked," she added. "It was the best thing we got out of those relationships."
What have they said about the friendship?
In a 2009 interview with Seventeen, Gomez was asked who she turns to for love advice, she said:
"Every single problem I ever have is healable by Taylor Swift," she said. "If I ever I have an issue, Taylor has gone through it, because she's older than me, and she gives the most thought-out answers. And what I love about Taylor is that she does believe in the whole love story and Prince Charming and soul mates. Because of her, I haven't lost faith. We literally talk every day."
In May 2014, Swift talked about why her relationship with Gomez was so special during an E! interview: "It's been the longest one I think either of us had really," she explained. "When your life changes, and you become thrust into this really strange whirlwind where what your life is is different from what other people think your life is. And your life is commented on and your life is written about and fictionalized and all that. Both of us have kind of stuck it out and hung in there through all the different changes we've gone through." Swift added, "Longevity is something you really can find very precious and rare in friendships."
A source told E! in January 2019 that Gomez "really leans on Taylor and considers her one of her best friends," particularly in the aftermath of her treatment for her mental health:
"Selena and Taylor have been in touch since Selena left her treatment and are very close," the source added. "Taylor has reached out several times and has shown her support and love." The two are in a "really good place" and remain close despite consistent travel for work.
After the late October 2019 release of Gomez's new single "Lose You to Love Me," Swift praised the song on Instagram. "This song is a perfect expression of healing and my absolute favorite song she's put out yet. A triumph," Swift wrote on her stories, which Gomez posted to her own.
Swift also expressed her excitement during an interview on New Music Daily With Zane Lowe on Apple Music’s Beats 1:"She came over, she played me the video. I'm so proud of her," she said. "She's been through so much. I've watched so much happen in her life and had a front row seat to so much, and I'm so proud of her. She is such a revelation because now she's making her best stuff."
A a few days later when Gomez seemingly plugged Kim Kardashian's SKIMS shapewear line on IG stories. "Legit so freaking comfortable @skims," she wrote over a photo of herself wearing a pair.

Hours later, that photo had been taken down and replaced with a Swift appreciation post. "My ride or die. I would die for this one," Gomez wrote over a selfie of the pair and one of Swift's cats. "Thank you for being by my side. You have taught me so much, walked through all of this with me, STAYED and you remind me to be a better human being. I'm on your side for life."

Selena stands up for Taylor:
When Kim released the video of Taylor and Kanye and the whole internet was calling her a snake, Selena had this to say:
There are more important things to talk about... Why can't people use their voice for something that fucking matters?
— Selena Gomez (@selenagomez) July 18, 2016
Truth is last thing we need right now is hate, in any form
— Selena Gomez (@selenagomez) July 18, 2016
This industry is so disappointing yet the most influential smh
— Selena Gomez (@selenagomez) July 18, 2016
Re: Taylor's masters:

Taylor's genuine, candid disgust for Selena's ex

Demi, Taylor, Selena
I'm in love..... #daylenapic.twitter.com/bOKpHUzOrb
— ㅤㅤㅤㅤㅤㅤㅤَ (@speaknowhoe) March 6, 2014
Selena and Demi Lovato had been friends since they met when they were kid actors on Barney & Friends but apparently stopped being friends because of Taylor Swift, but is this true?
I don't know exactly how they all became friends, but Taylor, Selena, Demi, AND Miley Cyrus were all a squad at some point and hung out. They all dated Jonas Brothers at one time or another so I think that was the common link. Taylor also starred in the Hannah Montana movie with Miley produced by Disney. At some point they all stopped hanging out as a group and from what I can recall I think it was because of the Jonas Brothers lol (I'm sure someone in the comments will have receipts). This was also around the time of the infamous YouTube video beef. Selena and Demi would make Youtube videos with one another and Miley and her older friend Mandy openly mocked one of Selena and Demi's videos
At some point though, Selena and Demi stopped being friends and according to Demi herself it was because of Taylor:
OP NOTE: I personally think Selena and Demi drifted apart because of Demi's partying/ emerging substance abuse issues and it seems like Taylor and Selena were always close, so maybe Demi just felt replaced and blamed it on Taylor. What do you think ONTD?
Taylor and Selena through the years







Source: 1, 2ask taylor, miley/mandy/selena/demi, selena 1, selena 2, selena 3
ONTD, why do you think Taylor and Selena have remained such good friends for 13 years while being two of the biggest pop stars in the world?