I'm another lady that travels regularly as a solo - both for business and leisure - and have no reservations in doing so. I'm mostly limited to the Y cabin, but I have recently managed to get to WP on the back of all that Y travel, so I do enjoy the flounge. Being one of only a few in the flounge is not threatening - you get the odd curious look, but generally everyone is doing their own quiet thing.
I think, as others have mentioned, the main reason for the lack of solo female travellers is the family issue - whilst their blokes are out on the road, the Mums are at home with the kids. This not only means they are tied to the kids at home, but their careers are also affected, meaning the number of ladies in higher level roles is reduced - hence fewer numbers of solo ladies travelling for business.
I think, as others have mentioned, the main reason for the lack of solo female travellers is the family issue - whilst their blokes are out on the road, the Mums are at home with the kids. This not only means they are tied to the kids at home, but their careers are also affected, meaning the number of ladies in higher level roles is reduced - hence fewer numbers of solo ladies travelling for business.