R&B star Solange Knowles is holding a bedside vigil for a friend and business partner who is in a critical condition after a stabbing.

Armina Mussa is fighting for her life in a New Orleans, Louisiana hospital after she was allegedly attacked by a friend of her roommate on Wednesday (08Apr15).

Mussa reportedly became embroiled in a heated argument with Arronesia Christophe, who is accused of pulling a knife and stabbing the 24 year old repeatedly.

Christophe, 26, was arrested and has since been arraigned on charges of attempted second degree murder and aggravated battery. She is being held on $50,000 bail.

She told police she was attacked by Mussa and acted in self-defence.

Beyonce's sister left Los Angeles and flew back to her adopted home of New Orleans as soon as she heard the news, and she was in court for Christophe's arraignment hearing on Thursday afternoon (09Apr15), her representative tells USA Today.

Mussa is the project director for Knowles' brand Saint Heron and co-owns the Exodus Goods clothing boutique in New Orleans.