Cops said they were called to a home at around 10pm where they discovered the bloody scene and the corpse of the victim, San Antonio Express News reported.
The woman admitted to tying the man up and going after him with the power tool, KSAT reported.
Court records show that police had been called to the property where the man was killed 11 times last year.
Villegas has been charged with first-degree murder and was detained at Bexar County Jail on a $250,000 bond.
Authorities have not yet confirmed the relationship between Villegas and the victim.