Took Plan B last cycle, now late period.

My partner took plan b at 19th jan after we had non penetrative sex. I did not ejaculate and it was mostly foreplay. She wanted to take the plan B anyways, as she usually has irregular periods, and wanted plan B as to give her a peace of mind. 24th jan she did a pregnancy test which came out negative. 29th jan she had her period, which is due at that day, but it was lighter than usual, probably due to the plan b and lasted 4 days. Around mid february she had brown spotting, which was normal as sometimes she has mid cycle spotting, then around the time she was due for period (26th feb) she instead had a lot of clear white discharge, which stained her underwear. The following days there are only small amounts of white discharge and it was whiter. She also had PMS symptoms like lower back pain, cramps and sensitive breasts. she has history of having irregular/missed periods. It is 5th march and she is 7 days late. Could she be pregnant? Or is this just a side effect of the plan b?