Mumsnet user 'Thebrowntrout' said the toddler's screaming was "hard on the ears" and claimed the little girl always wanted things "immediately".
"She demands to be carried everywhere, won't go in the pushchair and my friend has a younger daughter as well who is nine months and is generally carried in a sling or pushchair," the user wrote.
"So either friend has to struggle and stagger with the weight of two children or carry one on her hip with the other in the pushchair."
"Am I being unreasonable to dislike my friends' daughter?" the user continued.
"The younger child is pretty much ignored since friend is constantly dealing with older one, and you can't talk to friend at all due to behaviour of child one.
"When do they behave like humans? This child will be starting school in 16 months and surely won't be behaving like this then?"
The original poster confessed she didn't have children and said she "admired" her friends' calm parenting skills.
The question was posted on the forum on 22 April 2016 and now has nearly 400 comments from parents, the majority who disagreed with her comments.
"You are being unreasonable," Mumsnet user Arsenicinthesugarbowl wrote.
"You're judging her parenting - I'm sure she isn't enjoying the situation either.
"Be a friend to her or don't see her anymore if you find it that stressful. Or see her without the kids."
Another person wrote: "Do you have or have you had a three-year-old?
"They're hard work and she sounds particularly so.
"Have you offered a helping hand to her mum, your friend? She sounds like she could do with your support rather than you writing judgmental posts on internet."
Other parents were offended by the comments about the child not being human.
"Screaming and behaviour issues don't make a child 'not human'," one person commented.
"You sound very judgemental and critical of your friend."
There were, however, some parents that came to the woman's defence.
Trying to find an explanation for the woman's post, one user argued that it wasn't the child she didn't like but the child's behaviour.
They suggested she was "jealous" of how much time the three-year-old was demanding of her friend.
"Young children have no perspective," the user tried to explain. "If her mum spends four hours playing with her and 10 minutes dealing with the baby it will be the 10 minutes with the baby that will stick in her mind and make her think she's been left alone."
Another user agreed: "You've worded it badly. You don't dislike the three-year-old but you dislike being in her company. That's reasonable. Some small children's behaviour can be unbearable!
"Avoiding her is cruel, but offering unsolicited advice is awful."
The original user responded to comments, saying: "I don't say anything to my friend and I smile brightly and attempt to cheerily engage with the child and just accept we can't talk about anything.
"But inside I am thinking 'stfu, brat'."