Female Phenotype Theory (FPT) suggests that autistic women often present with less obvious social impairments than autistic men. We examined the possibility of an exaggerated female phenotype among undiagnosed but probably autistic women. In two nationwide online surveys, we compared self-reported social functioning and mental health between diagnosed autistic women and women without diagnosis who scored ≥ 32 on the Autism Quotient. Compared to diagnosed autistic women, probably autistic women had higher empathy and general social functioning, and were more likely to have received a diagnosis of Borderline Personality Disorder. Autistic women had typically received more mental health diagnoses prior to their ASC diagnosis than autistic men. These findings shed light on the history of misdiagnosis experienced by many autistic women.