Stacey Eden said she pulled out her camera phone after witnessing "a good 10 minutes" of abuse from a woman wearing red floral pants on a CityRail train travelling from Town Hall to the airport about 1.40pm on Wednesday.

Ms Eden's footage begins with the woman in red saying to a woman in a hijab opposite her: "Why do you wear it for a man that marries a six year-old girl?"

The Muslim woman, who is sitting with a bearded man and a baby in a pram, does not respond.

Ms Eden interjects to say: "She wears it for herself, OK? She wears it because she wants to be modest with her body, not because of people like you who are going to sit there and disrespect her."

The abusive passenger then brings up the Lindt cafe siege in Martin Place and says to the woman: "Your kids behead people."

"That's not her doing it. That's a minority of people, not a majority of people," says Ms Eden, growing increasingly angry at the abusive passenger.

When the woman in red mentions "148 Christians murdered in Kenya" and Muslims murdering each other in Syria, Ms Eden responds "What's that got to do with this lady?"

The passenger responds with "Nothing, you're the one that started the argument."

Ms Eden told the woman she started the argument by saying things under her breath and tells her, "If you've got nothing nice to say, don't say anything, it's simple."

Ms Eden uploaded the video to her Facebook page on Wednesday evening and said she was stunned when it instantly attracted thousands of likes and comments, mostly from people telling her she was a legend and a hero for defending the woman.

"Wow I respect u so much for defending our beautiful religion," one Facebook user, Rawa Homsi, posted online.

"Good on you girl. Poor lady is sitting there with her husband and baby minding her own business, probably crying her eyes out at home right now," said another user, Mariah Armani. "I respect you for standing up for her while everyone turns a blind eye."

Another user, Fatima Krayen, said: "There are beautiful people still out there, respect to you for speaking up. It may not be a big deal to U or others watching. But to that lady that U spoke up for it would have meant the world. Take my hat off to you."

Ms Eden said on Thursday that she was overwhelmed by the response.

"I genuinely have tears in my eyes at the messages people have sent me," she said. "I didn't realise how something so small would end up being so important."

Ms Eden told her Facebook friends that it took "everything in me to hold back on this woman, she made me soo angry! I had to actually stop myself before i got too worked up."

She said she wasn't sure what response she'd get from others on the train carriage but she felt compelled to say something because it seemed that the Muslim woman and her husband were too scared.

"I just wanted to tell her that what she was saying wasn't OK," she said.

"The point of this is, don't sit there putting someone down because they are wearing a scarf, she never did anything, she sat there and didn't say a word, but I can only imagine how she was feeling inside."

Mariam Veiszadeh, founder of Islamophobia Register Australia, said she was "heartened" by Ms Eden's actions but said it was still rare for bystanders to intervene in such incidents.

She said the number of incidents reported to the register hasd increased following the Reclaim Australia rallies around Australia this month.

"We're not in the midst of an imaginary backlash, Islamophobia is very much real and you can see from the video it has devastating consequences for Muslim women," she said.