Zafreen Khadam, 32, told Sheffield Crown Court she did not support terrorism and posted the links in order to "put myself in their little world".
Prosecutors claim the posts, which included execution videos, "glorified" IS and "encouraged terrorism".
Miss Khadam, of Vincent Road, Sheffield, denies the charges.
She said she had become interested in finding out more about IS after reading an article about a footballer who had joined the group.
She said she had been working with Sheffield-based group Football Unites Racism Divides and running a football blog at the time.
"There was an article saying 'London footballer leaves to join ISIS' and that really attracted me because it said football and London," she said.
"I read about him but then I did not know what ISIS was, what's an ISIS? where's he going? That's when I started looking in to it."
The court previously heard how Miss Khadam had described Kuwaiti-born Mohammed Emwazi - nicknamed "Jihadi John" - as "kind of scary" but said she "would marry him".
Asked by her barrister, Dermot Hughes, why she had begun posting links relating to IS on Twitter, she said: "I wanted to know more about these people and why would people that like football want to go across, so I put myself in their little world."
Mr Hughes then asked if she wanted to be a "paid-up, card carrying member of IS" to which she replied: "It was always about understanding them. I never supported them in my heart. It was an act."
Miss Khadam is said to have set up 14 Twitter accounts and used online messaging service Whatsapp to share pro-IS videos, documents and speeches.
She denies ten charges of disseminating terrorist publications between February and March 2015.
The trial continues.
A woman accused of encouraging terrorism by sharing so-called Islamic State propaganda online has said it was an "act" to "learn more about ISIS".