Having already experienced two pregnancies, she said she was consistently strict with foods and was aware of the risks and of what she could and could not eat.
After the embarrassing encounter, Shell refused the decaffeinated coffee and asked for a refund, before taking her children home to make her own coffee.
"I was just so shocked and angry because I really wanted that coffee – it was midday at that point," she said.
"I felt a bit judged for my choices, it just felt a bit unfair that someone else was making assumptions based on my pregnancy.
"I've always drunk coffee, in fact nowadays I need it more and more, but I do try to just stick to the one and I'm pretty strict with other foods as well."
Following the ordeal, Shell's husband Tim got in touch with the cafe to share his disappointment, prompting a response from the owner of the cafe, who apologised for the incident.
In a message to the couple, the owner said the staff had made an incorrect decision and that it wasn't store policy to refuse service.
The owner invited the duo back to the cafe for free drinks, but Shell said she wouldn't return.
"We were happy with the response but I won't be going back, even though they offered coffee," she said.