How old is the singer from American rejects?

You're likely referring to Hayley Williams, the lead singer of the band Paramore.

Hayley Williams was born on December 27, 1988, making her 34 years old as of October 26, 2023.

It's important to note that "American Rejects" is another band, and while their lead singer Tyson Ritter is also a well-known musician, he's not related to Paramore or Hayley Williams.