The "True Grit" star appeared in the video for Swift's "Bad Blood", which was aimed at Perry, but insists she never wanted to appear to be against the "Roar" singer, and she was thrilled when the two pop stars patched up their differences and appeared together in Taylor's "You Need to Calm Down" promo.
"I actually thought it was incredible," Hailee tells "Watch What Happens Live". "I loved being a part of the 'Bad Blood' video... and her latest video with Katy is amazing."
"It was so fun to see it. It's the most incredible video to watch... and to have ended on a moment like that, I thought was really special. They are two of my favourite people, so I'm very happy that that all happened."
At the end of the promo, Taylor and Katy - dressed up as fries and a burger - embrace as pals.
The two stars initially fell out when Katy nabbed Taylor's dancers for a tour. Their feud lasted for three years before Katy reached out to end the pop stand-off.