Jane Fonda Feels 'Good' Ahead of Milestone 85th Birthday: 'I Feel Very Strong'

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Jane Fonda is in a partying mood as she prepares to turn 85 on Dec. 21.

The activist and Academy Award winner told PEOPLE she felt "very strong" before she rang in her milestone birthday on Thursday in Atlanta with a celebration that raised more than $1 million for the Georgia Campaign for Adolescent Power & Potential (GCAPP), the teen pregnancy prevention and adolescent health organization she founded in 1995.

After announcing in September that she was diagnosed with a "very treatable" cancer, non-Hodgkin's lymphoma, Fonda said this week that she's "halfway through" her chemotherapy, which is "easier than a lot of other" treatments.

RELATED: Jane Fonda Wants to Give Young People Hope They 'Will Have a Future' as She Turns 85

"I'm not losing my hair. I don't feel nauseous," she noted. "The week when I get the chemo is hard, but then after that, I feel good. I feel very strong."

Fonda admitted at Thursday's event that she was "just a little weak from the chemo, but I feel great" as comedian host Heather McMahan escorted her onstage.

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"I've lived a good life. I've lived a productive and intentional life," she told PEOPLE a few days ahead of the event. "And dying is part of life. I hope that I can be an example to young people so they won't be afraid of getting older."

"But you just have to take care of yourself, which I do even now. Even the days that I get chemo, I still do a workout. It's slow and not what it used to be, but still, I'm moving and keeping strong," Fonda explained.

The Grace and Frankie star has worked to provide Georgia youth with comprehensive age-appropriate sex education, among other services, since launching GCAPP in 1995. Just as she did when turning 80 and 75, Fonda used her 85th birthday to shine a light on the organization with Thursday's event at the Pink Castle, a private residence in Buckhead.

Fonda sat in a seat adorned with flowers as she thanked Tyler Perry and Ludacris for joining her at the celebration, where guests enjoyed a performance by Gladys Knight. Also in attendance were Abby Wambach, Glennon Doyle, Catherine Keener, Sanjay Gupta and wife Rebecca, Sara Blakely and the Indigo Girls' Emily Saliers.

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As friends toasted to the birthday girl throughout the event, Fonda was also surprised with video messages from the likes of Chelsea Handler, Stephen Colbert, Jimmy Kimmel, Helen Mirren, Glenn Close, Demi Lovato, Eva Longoria, Diane Lane, Sally Field, Elle Fanning, Gloria Steinem, Tom Brady, Snoop Dogg, Lionel Richie, Harry Belafonte, Nicole Richie, Salma Hayek, Amber Valletta, Taylor Schilling and Jeff Bridges.

RELATED: Jane Fonda, 84, Diagnosed with 'Very Treatable' Cancer and Is Undergoing Chemo: 'I Feel Very Lucky'

Dolly Parton said in one video message: "Jane, I just wanted to say happy birthday to you. I am not even going to say the number because nobody believes it anyway. I wish I could be with you in Georgia."

Whoopi Goldberg told Fonda in another clip: "Don't need to know how old you are because you are timeless. You have always been a big light in my life and I wanted to make sure that I said to you, 'Happy birthday. Enjoy and happy joy.'"

Leonardo DiCaprio also gave a virtual shout-out. "So sorry I couldn't be there tonight. Happy 85th birthday. You have given so much to the world, inspired millions of people, generations of people to become activists and leaders. You have inspired me and so many others. So, this is just to tell you happy birthday and good health," he said.

The cocktail hour was followed by a live auction in which Fonda invited one high bidder to have drinks with her at her home, noting: "And I won't be on chemo so I will be having a lot of drinks." The winner will also get to join her in January at the red carpet premiere of 80 for Brady, the upcoming movie in which she stars with Brady, Field, Rita Moreno and Lily Tomlin.

RELATED VIDEO: Lily Tomlin Calls Jane Fonda 'Indomitable' After Cancer Diagnosis: 'She's Very Forthright' About It

Ahead of Fonda's birthday party, she credited her family with motivating her to continue doing the work as an activist, telling PEOPLE: "I just want my young grandchildren to know that grandma did her best."

"It's going to be rough for young people, and I just want my kids to know and my grandkids to know that I did my best," Fonda added.

Fans can celebrate Jane Fonda's 85th birthday with a donation to GCAPP.