According to TMZ's report, Lovato had allegedly set Lambert as the opening act for her upcoming world tour, but ended up giving his slot to pal Nick Jonas instead.
"Nick is one of my best friends and also business partners," she said on Saturday, neither confirming nor denying the speculation.
Earlier this year, Jonas and Lovato teamed up as co-owners on a new record label, Safehouse Records. Their friendship dates back to the pair's Disney days. The duo first shared the screen in Disney Channel's Camp Rock back in 2008, and their respective series on the network -- Lovato starred in Sonny with a Chance, and Jonas in Jonas -- each aired shortly thereafter.