The pregnant singer - who recently announced she was recording again after retiring in 2009 - flew out to Los Angeles to perform a duet of `True Love` with Pink at a secret show at Sony Studios and had a great time on the whirlwind trip.
Lily - who has an eight-month-old daughter Ethel with husband Sam Cooper - said: "It was great, felt strange being back on stag again but Pink made me feel at ease. Really enjoyed myself though. Can`t wait to get back out there."
Though `True Love` appears on Pink`s forthcoming new album `The Truth About Love`, the recording of `VH1 Storytellers` was the first time the US star - who has 14-month-old daughter Willow with husband Carey Hart - had met Lily and the pair quickly bonded over their love of music and their children.
A source told the Daily Mirror newspaper: "It was the first time they`d met, though they`ve spoken on the phone and emailed before. They`re huge fans of each other`s music, so Lily was thrilled when Pink asked her to get involved with her new album.
"Lily is five months pregnant and Pink told her she couldn`t believe how amazing Lily looked, and that she could still manage to wear heels while that far gone.
"They were comparing notes about parenthood, too, as both their daughters are about the same age, and had a lengthy discussion about prams.