It's the same way a woman might feel uncomfortable at a bar or party full of drunk guys with no or few other women present. It doesn't mean she has a problem with or is intimated by any particular man there, or alcohol, or men in general. The combination of a stark gender imbalance and the de-inhibiting effects of alcohol can create a testosterone charged atmosphere, especially if many of the men are young and single, and it simply isn't pleasant for someone outside that mold to be part of.