Susan Wojcicki said being hurtful "wasn’t our intention at all."
Staffers have been negotiating with the company for 14 months.
CEO Jim Bankoff, meanwhile, said he was disappointed in the walkout and said paying higher wages was "not realistic or smart."
The social media giant previously told Vox's Carlos Maza that "deeply offensive" opinions don't violate its anti-harassment policies.
Lockhart Steele was fired from Vox Media last year after an incident of forcible kissing.
Employees will instead receive two drink tickets, the company said in an internal email sent out Thursday afternoon.
The digital firm owns several sites, including Vox.com, SB Nation and Eater.
"By cancelling the panel, SXSW has assisted those who wish to silence women by threatening violence."