Emergency services were called to Dobu Place in Glenfield just before 5.30pm yesterday following reports of a violent incident.
When they arrived, they found a 44-year-old man with a slash wound to his left thigh, while his 47-year-old partner had received a less serious cut to her head.
The couple were taken to Campbelltown Hospital for treatment.
Police search the area and initially arrested three women, but two have since been released without charge pending further inquiries.
The third woman, aged 36, was held overnight and this morning charged with wounding a person with the intent to cause grievous bodily harm.
She has been refused bail to appear in Parramatta Local Court today.
Police say an “improvised weapon” has been seized at the crime scene and will be examined by their forensics team.