The remaining four members of the group - Nicola Roberts, Kimberley Walsh, Nadine Coyle and Sarah Harding - are expected to attend the star's headline show at London's O2 Arena on October 7.
"The girls are all coming - they don't know about the medley yet, though," Cole told the Daily Star. "We haven't been together in a long time."
The outing will mark one of the few occasions Girls Aloud have been together as a five-piece during the last few years, and comes weeks ahead of their imminent 10th anniversary reunion.
Meanwhile, Cole also joked about her first-show mishaps during her opening date in Belfast earlier this week.
"Did anybody see me rip my trousers? Look at them. I've even got a safety pin in the back," she said.
The star's new boyfriend - American dancer Tre Holloway - had to pull out of performing on the 'A Million Lights' tour after damaging his knee in rehearsals.
"He did it on the trampoline - the one I told him not to bounce on," Cole said. Tre added: "It's not a cruciate ligament injury, so I'll be back soon."
Cole continued: "It's amazing, seeing all the things that go wrong. I was supposed to have an extra two boys next to me dancing, but that changed. I was looking around thinking, 'Where have they gone?'"
Meanwhile, it was recently reported that Girls Aloud will release a brand new single next month.
Click through our gallery of Cheryl Cole's 'A Million Lights' tour below: