Nicola Manning, of Laburnum Close, Barry, pleaded guilty to stalking at Cardiff Magistrates Court on March 13.
The court heard how Manning, 31, placed a tracking device on her victim’s vehicle and monitored his movements, and placed a listening device in his bedroom at his property.
Manning also went to the home addresses of women associated with the victim.
The incidents took place between January 2022 and September 2022 in areas of South Wales.
Manning pleaded guilty to one charge of stalking without fear, alarm, or distress.
She will be sentenced at Cardiff Magistrates Court on April 25.
She was released on unconditional bail.