Shots were fired — both in ‘Rolling Stone’ magazine and on Twitter — and now we know why! A source explains EXCLUSIVELY why Katy isn’t a fan of the ‘Shake It Off’ singer. Katy Perry doesn’t appear to be too happy with Taylor Swift for allegedly calling her out in a new Rolling Stone interview, featured in the Sept. 25 issue. But a source tells EXCLUSIVELY that their relationship has been strained for quite some time — find out why! Why Katy Perry Dislikes Taylor Swift !! “Katy and Taylor are the definition of oil and water. They both have completely opposite personalities and Taylor just rubs Katy the wrong way. Katy feels that everything Taylor does is completely fake and annoying and she really doesn’t care for her,” a source tells EXCLUSIVELY . So why all the bad blood? Well, both singers dated John Mayer – Katy after Taylor. Enough said, right? “Katy has had many talks with and heard stories...