Swift was performing at the Gillette Stadium when she invited the singer out to perform her single.
“UM @hayleykiyoko THAT WAS INSANE!,” wrote Swift on Twitter along with video footage of their duet. “Thank you so much for coming to surprise the crowd tonight at @gillettestadium – THAT WAS SO MUCH FUN!!!! So stoked this was your first stadium performance, and you absolutely killed it ?????????????.”
“We should applaud artists who are brave enough to tell their honest romantic narrative through their art, and the fact is that I’ve never encountered homophobia and she has,” wrote Swift.
“It’s her right to call out anyone who has double standards about gay vs straight love interests.”
Kiyoko made headlines last month when she spoke out about her experience of coming out – and how a fan helped her.
“I came out to her and said, ‘I just want to sing about being cocky and stealing someone’s girl, because that’s my dream.’ She told me to write about it.”
Kiyoko added that she was surprised by the amount of positivity within the track’s comments section. “I was shocked at how people weren’t judging me,” she said. “I was ready to be judged, and I was ready to be labelled.
“That was a moment for me where I was like, I can be myself and people are okay with that.”