Hello,
Yes, it is definitely you have to be concerned about.
Birth pills are hormones that help in preventing pregnancy by acting on endometrial and ovaries. They are meant to be taken regularly and every day. It is not meant to be taken 5 pills on one day. The missed pills have caused severe withdrawal bleeding with stomach cramps.
She will have irregular periods for a while, can't exactly tell when her irregular periods will stabilize. I suggest she just waits and not take anything, in specific I mean birth pills. As if she takes birth pills her condition will worsen.
If she continues to have withdrawal bleeding, I suggest you visit a gynecologist who will ask for USG pelvis.
Thank you.