(song starts around 1:08) Currently on tour, Clarkson is known for often doing a one off cover on each night of her tour. On a recent night in WI she covered "Shallow" by Lady Gaga from A Star Is Born.
She briefly speaks about how kind Lady Gaga is, and how early in Gaga's career they both did a show together and Gaga wrote Kelly a hand written thank you note. OP suspects she is talking about a House Of Blues concert they did together in 2009. OP Thinks Kelly sounds flawless but can work on her HOOO OHHH OHHH OHHHHHH.