The 'American Idol' finalist - who shocked viewers when she was booted off the show at ninth place, despite being a favourite to win - is set to perform on the reality talent competition while her rumoured boyfriend Mark Ballas does a routine with Karina Smirnoff.
The professional dancer, 24, wouldn't disclose what song Pia will be singing but revealed it will be "slow and romantic".
He told Us Weekly: "I get to dance with Karina and Pia will be singing, which will be amazing because she's a ridiculously amazing vocalist."
Although the couple are keeping tight-lipped about their reported romance they were spotted having dinner together twice earlier this month, where an onlooker said they "spent the whole day flirting."
A friend of Mark's said: "Mark isn't hooking up with her - yet! But he will, if he gets his way. She is totally his type: gorgeous and a musician."