With difficulty and trepidation. You basically have to be semi-closeted and learn about and look for red flags. Transbians (unlike some homosexual transsexual males) almost never pass in photos much less in real life, but women are also socialized to ignore red flags and be kind and non-judgmental. There was a story on TL or GC on Reddit where a lesbian matched with a transbian who went to great lengths to lie about being trans. She saw red flags and ignored them to be sympathetic but was finally faced with incontrovertible evidence during that first encounter which took place in her home. But because of the physical and political power imbalance, she also did not feel like she could say anything to call out this behavior and still had to play nice to get him out of her home. It’s frightening, honestly.