The hitmakers' overblown rift began when Swift 'liked' a fan's Tumblr post about the effort she makes at backstage meet-and-greet sessions versus those staged by more awkward stars, like Lavigne.

Lavigne picked up on the blast and tweeted, "Comparison is judging and judging a person does not define who they are it defines who you are. We all Love our fans."

The Canadian singer then posted a photo collage of her posing with happy fans, adding, "So let's keep it all about the love and stay positive."

It appeared any 'beef' between the two young women had been resolved by the time they hit the stage together on Saturday during Swift's concert at Petco Park.

They performed Lavigne's 2002 hit Complicated and Swift later wrote on Twitter.com, "So incredible sharing the stage with @AvrilLavigne! 'Complicated' is such a brilliant pop song and I just love her."

Swift also welcomed Jamaican singer OMI to the stage for a performance of his chart-topping reggae anthem Cheerleader.