When you travel alone or with a single male friend if you get approached by a girl and she asks you to pay her a drink don't do it. There is a chance that when you finish the night you will have a really high bill. Unless the prices are clear and you order yourself. If the girls come out of nowhere there is a chance that she works in the bar too and some places can charge you for "service fee". If you end up falling for this scam just try to contact a friend outside or the tourist police. Try to gain some time. If you feel you can do anything just pay with credit card and then ask chargeback after you go to the police.