Why on earth would that be true? No. I don't have a problem with betting 或者 bet shops (my brother bets regularly), but it's rarely got a girl in it because girls can think of 更多 sensible ways to spend their money on a 日 to 日 basis. It's fine if 你 only do it once in a while. The men that go in their, go often and gamble away all their money, unlike some girls that only go in their every so often.
Girls have as much money and as much chance in winning as boys do, and it's not exactly a shocking place to be if you're over the age limit, so there's no reason for it not to be a place for girls.
你 should stare right back at them and beat all their butts 由 winning 更多 money than them ;) that's probably the best thing to do.