The 52-year-old singer - who was part of the iconic girl group alongside Mel B (Brown), Emma Bunton, Geri Halliwell-Horner and Victoria Beckham - has insisted plans to mark the occasion seem "closer" than they did before.
During an appearance on The Rebecca Judd Show on Apple Music 1, she said: "Okay, we're closer in that Emma's rooting for it too!
"You know what, I'm not going to throw anybody under the bus. We all are so proud, of course we are, of our legacy. It's amazing.
"And it is 30 years and we do have to celebrate that in some way this year. I'm always optimistic."
The Wannabe hitmakers last performed as a fivesome at the London 2012 Olympic Games Closing Ceremony, and without fashion designer Beckham in 2019 because she wanted to focus on her family and her business.
Chisholm admitted she and Brown have been leading the charge for potential celebrations, but she said the group all feel some pressure about doing things "the wrong way".
She added: "I think me and Mel B are the cheerleaders and Emma's totally with us, but we all love it so much.
"I think it's so precious to us. We're frightened to do it the wrong way. Do you know what I mean?
"So it's like we're still working, we're always talking, lines of communication are open and we are just waiting until we all decide on exactly the best way to do it."
In September last year, Beckham - nicknamed Posh Spice - hinted that she wanted to reunite with her former bandmates after attending Oasis Live '25 tour show at Wembley Stadium, with her 50-year-old husband, former professional footballer David Beckham, and their children Romeo Beckham, 23, Cruz Beckham, 20, and 14 year old Harper Beckham.
Captioning one clip at the time, she wrote: "Tempting," and tagged her bandmates.
Fellow 1990s pop icon Robbie Williams has also hinted a reunion with Take That might also be on the cards.
The Angels crooner - who famously dated Halliwell-Horner when they were at the peak of their fame - left the legendary boy band in the mid-90s before embarking on a hugely successful solo career.
As the remaining members of Take That - Gary Barlow, Howard Donald and Mark Owen - announced their revival of The Circus tour, Williams says he wouldn't rule out a reunion.
Appearing on BBC Radio 2, Williams told presenter Scott Mills: "Would I return to Take That to do the Circus again? I did love it last time.
"Not right now. I'm sure we'll all ride again, but it's not in my plans."
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