In practice, it’s mostly about in-group signalling.

But the idea was to emphasise the physical aspects of power/discrimination. It’s not a pure synonym for person. It should be used when you are talking about something where the actual body is particularly relevant. That’s mostly when you want to emphasise physical assault.

It works here, because she feels at risk not because she’s female in her head, but because she’s likely smaller/weaker or perhaps “looks” like a target. She’s a person wandering around in a female body, and is therefore has different risks than a person wandering around in a male body. (Actually debatable which one is at higher risk overall, depends on circumstances.)