The singer, 24, counts Girls star and author Lena Dunham, singer Lorde and actress Jaime King among her inner circle.
The creative, close-knit group is "the most important thing to me right now," Swift tells PEOPLE in this week's 40th anniversary cover story.
"They are trustworthy and know me and like me for who I actually am," says Swift, whose new album, 1989, drops Oct. 27. (Pre-order it here.)
An avid hostess, Swift gathered some of her best friends – including Emma Stone, King, Dunham and Jessica Szohr – for a fun-filled 4th of July get-together in Rhode Island this summer.
"We made a giant slip-and-slide in the yard, we were running around the beach, jumping into the pool, cooked a giant dinner and played games," says the Grammy winner.
"Everybody in the group was so happy. Seeing your friends all together, and seeing your friends bond and everyone smiling and laughing together was the coolest thing I could have expected of that trip."
"She plays new songs she's heard, and we play each other new music we've written," says Swift.
With Hart of Dixie star King, 35, we "sit around and talk and cook, or just order in Chinese food," she says.
"My friends aren't really much for going out to bars or clubs. They're not really as interested in that – and I'm not, either – so it works out pretty well."
For much more from Swift, pick up this week's special 40th anniversary issue of PEOPLE, on newsstands Friday. And flip the magazine over for even more from your favorite stars, including life lessons from Julia Roberts, Kerry Washington, Matthew McConaughey, Jennifer Aniston and First Lady Michelle Obama.