The jury at London's Snaresbrook Crown Court heard that, following the attack, Konye pretended to give Ms Oni a shoulder to cry on.
The court heard that the day after the attack, Konye sent a mobile phone message to her friend, who was in hospital receiving treatment, saying "OMG, I can't believe it."
The victim burst into tears as she left the courtroom and was hugged by family and friends.
She said as they left court that they were "glad that a truthful verdict had been reached".
Dressed in black, Konye remained calm as the jury of eight men and four women returned their unanimous verdict.
She will be sentenced on March 7, and Judge David Radford said: "I should make clear that, in my judgment, this is a case that will, in all likelihood, need a substantial custodial sentence.
"It is inevitable, but it won't be dealt with until I have received those (pre-sentence) reports." Speaking outside court afterwards, Detective Chief Inspector Dave Whellams said it had been a "serious, horrible offence which required a degree of planning and calculation".
He told reporters that witnesses had testified in the court that the attack had been planned over the course of two years.
He said: "Mary Konye has had to purchase, at some point, some sulphuric acid.
"She has prepared for this over a number of months, even years, all resulting from a trivial, insignificant argument that everybody has in their everyday lives."
He commended Ms Oni as "a very brave woman and one I have great sympathy for."
Baljit Ubhey, Chief Crown Prosecutor in London, who described the attack as "extremely brutal," said: "Konye has now been brought to justice and must face the full consequences of her appalling actions.
"I would to like praise Naomi's courage and dignity in giving evidence during this trial."
- Independent
