I'd say the chances are very slim...while it's true you can get pregnant while on your period, it's not very likely. A woman is most fertile around ovulation; with regular cycles, ovulation usually occurs around 14 days after the first day of a period, sperm can survive up to 5 days if conditions are favorable, but that still puts you at cycle day 9, she'd be unlikely to be on her period still on day 9 and with irregular cycles, is likely to have delayed ovulation beyond day 14, I did ovulate as early as day 11 when I was tracking my cycles, but even so, if this happened the first 5 days of her cycle, you're probably in the clear and you didn't ejaculate in her anyway...see if she gets her period once she starts the placebo pills at the end of the pack...although, most women won't start their periods the first day of the placebo pills; when I was on the pill, it usually took me 3-4 days of placebo pills before I'd start my period. And pill periods are often much lighter in flow and shorter too so if her period is lighter this month, she shouldn't worry.