Girlfriend gets revenge on 'cheating boyfriend' by tasering his crotch
This is criminal battery.
They do it because they get away with it. Parity would require the police roll up on her, give her a nice temporary bracelet set, charge her, and give her a good 2000 hours of community service to be served based on a sliding scale related to her work schedule. But make it difficult, and onerous. Skip days result in double hours. Sickness must be documented by a physician acceptable to the state.
Both parties need to be subject to the same stringent standards in these cases.