The 27-year-old singer physically attacked her brother-in-law in an elevator at the bash at The Standard Hotel in New York on May 5 but, prior to lashing out at him, she was allegedly warning women to stay away from him.
A source told Us Magazine: ''Solange was yelling that anyone who gets close to Jay has to be warned and deal with her as a sister.''
The violent altercation between Jay and Solange began to escalate after the rapper and his wife Beyoncé - who have two-year-old daughter Blue Ivy together - tried to get the brunette beauty to leave the party.
A second insider said: ''Jay said something small to her along the lines of, 'You are out of line.' Solange was being a loudmouth and snapped at Jay trying to calm her down and get her out of there.''
Solange was caught on CCTV kicking and clawing the rapper, 44, before she stormed out of the venue with a disgruntled expression on her face.
Beyoncé followed her sibling out and joined her in an awaiting car, while Jay - whose real name is Shawn Carter - opted to travel alone.
The insider explained: ''Bey was just trying to keep the peace and get Solange home, which is why she went with Solange in the car.
''Both Bey and Jay were trying to handle the situation. Solange has been that way before, and Jay and Bey just wanted to get her out of there and home before she really caused a ruckus.''