There was a study that showed people could very consistently determine gender of a photograph just by looking at a crop of the lips or eye brows

https://www.sciencedaily.com/releases/2015/06/150622083201.htm

The contrast between lip and skin colour can quickly identify a person's gender, according to researchers at the University of Montreal's Department of Psychology. The brain also analyzes light reflection in the eye area, which provides much information but requires more time to be interpreted. Nicolas Dupuis-Roy and Professor Frédéric Gosselin came to this conclusion by asking 100 participants to guess the gender of 300 people after being shown different parts of their faces.

Three hundred full-portrait photographs, of Caucasian faces of both sexes, were collected from the Internet. Some of the women wore make-up, while all the men were clean shaven. No other gender-identifying signs such as clothing or jewellery were visible. "Many studies on the subject are limited in their validity. Some researchers have examined information extraction strategies on non-realistic pictures. Others have determined beforehand the facial areas to be studied or have used only grayscale images," explained Dupuis-Roy, who took care to avoid these methodological biases. Using the "bubbles" technique, the chromatic (colour) and achromatic (grey tones) content of the pictures was randomly sampled for 200 milliseconds, leaving only a portion of the visual information at a time. This method allowed the researcher to know precisely which facial areas were the most important for the task and when the information was extracted by the brain. As the facial areas were displayed, the 100 observers were simply asked "Is this the face of a man or woman?"

Analysis showed that achromatic information in the eye and eyebrow area and chromatic information in the mouth area were most significant in recognizing face gender. Colour data for the mouth area was quickly isolated by the brain, barely 12 milliseconds after each face was presented! "Information in this area is situated along the red-green chromatic axis," said Dupuis-Roy. "But contrast between the lips and skin is more pronounced in women than it is in men because their skin colour generally contains less red and therefore more green. This contrast is perceived by our brain as a female characteristic."

They even did analysis merely using lipstick prints on a piece of paper

SHOW MORE

I think she's wearing lipstick.

This forum will outlive her.

She will join the 42% within the year