Police arrived to find a 34-year-old man stabbed several times with a long, serrated butcher knife.
Witnesses said Teishawna Trimble, 25, stabbed the victim as she chased him through the complex. Complex employees and residents reportedly had to pull Trimble off the victim.
The victim was transported to UCI Medical Center in extremely critical condition. Police said the victim may not survive his wounds.
Police said the apartment complex's management had received previous disturbance calls caused by the couple.
The suspect and victim have lived at the complex for less than a year.
The suspect and victim's relationship was not clear. The victim had not been identified as of Thursday afternoon. The victim has a different last name than the suspect.