It's very easy:
when we meet a man she is interested in, she starts a subject on how much I work at office, that I am tired when I come back. Then she goes on stating, "I guess that he must be unable to fuck a woman since a long time. In any case not me as I prefer looking for better men..."
This is rather direct, but I must say that she has close to 2/3 of positive responses and even when a man seems not directly interested at first, it often appears that he will call later (when I am not in) to inquire on her day...