possible pregnancy? or regular Plan B symptoms?

My girlfriend and i had unprotected sex that resulted in me not pulling out. (a very dumb decision on both our parts.. :$ ). we did this without realizing she was about four or five days away from ovulation. The next morning she counted up the days, and decided to go and take the pill. So she had taken it within 12 hours or so. Within the next few days the regular symptoms started to arise. irregular bleeding, nausea, but no vomiting, and then tender swollen breasts came up about 5 days post consumption. These did not really concern me after doing alot of reading on this and other sites. so yesterday she said that her period was officially late, and then today it had shown up. now later today she says that it has become like the previous spotting again. only this time (as of so far) it has become "super light" without any cramping. Thats all that i have for now as far as info goes. could this be her period that was just affected by the intense hormones of the pill? Ive read on how it can change the flow greatly and the time at which it comes. i just would like some more insight and some responses from people who have been in this situation. I am very concerned about her and us in this whole situation. so please, any light shined would be greatly appreciated!! Also this is the first time she has taken anything like this and hardly ever takes any sort of medication. (barely even tylenol). with this in mind, i thought it possible shes having a much harsher reaction because of this? thanks again!