This merits a big "So What?" Some girls are sluts? Where'd you get the clue, Sherlock?
We all know promiscuity is wrong. But I guess it's especially offensive when done by women, because women are always expected to be more moral. Some folks here try to find practical reasons why sleeping around is wrong. Pregnancy, STDs, emotional damages are sited. But those are preventable things: we all heard about condoms, and getting drunk may offset mental/emotional stuff as well (plus there is great variation in level of emotional intensity among women). So, staying away from casual sex is not necessary for any material reason, it is not in any way a guarantee of a better marriage in future. Not sure about others, but I avoid such behaviors simply because G-d said so.