The little girl played the role of Anna Quinn, along with her twin sister Sophie.
In May the actress was diagnosed with acute lymphoblastic leukaemia.
She has since lost all her hair and is barely able to walk.
“It all happened so fast, she has had 3 blood transfusions then has had a bone marrow biopsy,” a fundraising webpage reads.
“Her treatment includes lots of different chemotherapy drugs.
“The side effects of all these drugs are brutal, she can barely walk at the minute and has lost all her hair.
“It's a long road ahead so with the help of our community we can all come together and do what we can to help the family.”
The family friend who set up the fundraiser has already smashed their target of £500, raising almost £5,000 for the young girl and her family.
Speaking to Belfast Live, Zoe’s mother Leah Brown said: "She's been in theatre so many times, she gets lumbar punctures to put chemo in her spinal fluid as well and that's done under anaesthetic.
"You never think your child is going to be in theatre at all and the last seven weeks, she has been in loads of times.
Discussing her daughter’s hair loss she said: "I know that's not the main concern, but it's the saddest wee bit for her.”
“Zoe just had the longest, thickest hair and it was the first thing anyone talked about when they saw her," she added.
The creator of Derry Girls, Lisa McGee sent her best wishes to the young girl, writing: "I am so sorry Zoe is going through this.
"She’s the most wonderful little girl and we are lucky to have her as part of our Derry Girls family.
"I’m sending her and her family strength and love”