During an Instagram Live video on Saturday, September 22, that has since been deleted, the "Back to You" singer was full of praise for her 28-year-old pal.
Replying to a fan who asked her how the "Shake It Off" hitmaker was doing, Selena replied: "How's Taylor? Taylor's awesome. I love her. She's amazing. I talked to her today. She's literally like my big sister, I tell her everything. She's so smart it freaks me out."
The 26-year-old also provided some healthy advice to fans who wanted guidance on how to get over an ex.
When asked about "how to forget someone" during the Q&A session, Selena seemingly touched upon her own experience of heartache, following her split from on-again/off-again beau Justin Bieber in March.
"You can't really just like forget someone," the brunette star answered. "You kind of have to just figure out why you're still holding on to them. Like why do you want to forget them? And then I think that's where you start. Ask yourself that question, like why do you want to forget them? And did they hurt you? And if they did, and it's not healthy for you to go back, or to that thought, that's not good."
Justin quickly moved on from his breakup with Selena, and reportedly popped the question to model Hailey Baldwin in July, just two months after rekindling their 2015 romance.
The couple is rumoured to be planning a wedding in Italy, after being spotted on holiday at the exclusive Belmond Hotel Caruso in Ravello.