Could she be pregnant if she used to take bc pills & then stopped & then took a day after pill for an emergency & now has had 2 periods in 1 month.?

Unlikely, but... Plan B and other emergency contraceptive pills can alter the menstrual cycle for the cycle in which the EC pill was taken, and sometimes the next cycle too. One should be sure to check a home pregnancy test about 3 weeks after sex, because an EC pill works most of the time, but not all the time.
Yes. It doesn't sound like she has perfect protection from pregnancy, so its possible she is pregnant. One thing she can do to find out is to do a home pregnancy test. Best wishes!