Okay so there are a few factors: 1- she was on her period 2- you didn't ejaculate in her. These two factors are enough to know you didn't get her pregnant with this encounter. Having said that, let me tell you that there is a theoretical possibility of pregnancy ANY time during a female's entire menstrual cycle, periods and all. Hence, using adequate protection at all times would be the best way forward.
Pre-ejaculate has very little chances of causing pregnancy even during the fertile period, so in this case I'd say it's none.