I don't believe we need to go into overscrutinizing how this woman responded TO A PERFECT STRANGER approaching her out of the blue asking her about her personal grooming habits.
Take it for what it is, let's stop overscrutinizing common sensical things and do what we can with the information we have.
I ASSUME, give benefit of the doubt, that the majority of people walking around is at least washing their hair on some regular basis (1nce a week, 1nce every 2 weeks, 1nce a month, etc.) so unless the OP stated she saw nit balls, smelled a foul odor coming from her hair and/or it looked very dandruffy and dusty - let's just give the woman the benefit of the doubt that the woman AT LEAST washes her hair and let's use common sense and stop being overly literal and make an assumption that if someone says they do nothing to their hair, that implies they are not going through major and complex beauty regimens to achieve their current length (whether short, medium or long).