According to MTV News, the Mean Girls star used her blog to accuse Ronson of being unfaithful and "breaking my heart".
One message directed at her lover read: "Please leave me alone and stop staying in the room below me. You've woken me and my mother up. Go to bed. Keep cheating, you win."
She later added: "I'm doing this publicly because you and your friends call Peoplemagazine... so, you win. You broke my heart. Now go away. I loved you."
However, E! News claimed that the couple are still in a relationship after they were spotted together at the Chateau Marmont in Los Angeles on Friday night.
Lindsay Lohan has revealed that she is "taking a brief break" from her romance with Samantha Ronson.
Speaking to E! News, the Mean Girls actress confirmed speculation that the couple have decided to part ways amid rumours that Ronson had been caught cheating.
"We are taking a brief break so I can focus on myself," said Lohan, who declined to give any more information.
Earlier, it was reported that Lohan had posted a string of messages on her Twitter account accusing her partner of being unfaithful. The 22-year-old is also thought to have been denied entry to a Ronson family party on Friday evening.