your ingrown hairs were most likely caused by your pubic shaving (called folliculitis barbae) not an occult vaginal infection from your partner. while skin bacteria can be spread in this way she would most likely have a similar skin infection no a vaginal infection that may be contributory.
can having sex with someone who has a vaginal infection give you ingrown hairs? . my girlfriend has a vaginal infection but we still had sex because she decided the pleasure outweighed the pain. later the next day i had a couple ingrown hairs among my pubic hairs. i do shave that area but this time i had shaved it into a heart and the ingrown hairs were among the already grown hairs rather than the shaved and none were outside of the previously grown area. there are five in total and i've never had more than one or two from shaving. so this time stood out to me.