hi there! im seeking for your advice.. thank you

i would like also to ask if the warrantless arrest was lawful.. my officemate was charged with the violation of RA 7610 sec 10 (a). the alleged victim was 17 years old.. the complainant and her grandmother was yelling foul words towards my officemate's sister. she confronted them until a heated argument ensued... the complainant (17 y/o) sustained abrasions, my officemate also sustained abrasions. After the incident, my officemate went to the barangay hall to report the incident.. but to her surprise the complainant was there already reporting the incident. The barangay tanods then did not permit my officemate to go home.. they brought her to the nearest police station.. she complained insisting that she should not be brought to the police station because she was at the barangay hall to report the incident.. but to no avail, she then brought to the police station.. after interviewing the alleged victim by the police investigator, my officemate was held for detention. We complained that she should not be detained because the arrest was not lawful, that she was at the barangay hall to report the incident.. But the investigator insisted that her arrest was considered without warrant/warrantless arrest.. my query is, was her detention lawful considering that her arrest was not lawful?