Brenda Delgado was detained at a house in the city of Torreon, in northern Coahuila state, the Attorney General's Office said yesterday.
She will be held at a Mexico City prison pending extradition proceedings. She faces charges of capital murder and unlawful flight to avoid prosecution in connection with the September death of Dr Kendra Hatcher, a dentist.
Hatcher, 35, was fatally shot in the parking garage of a Dallas apartment complex. Police have arrested the suspected gunman. Delgado is accused of hiring accomplices to carry out the hit.
The boyfriend had dated Delgado for about two years before his relationship with Hatcher.
