Bolded part is very true.

Just to share again to MangoTax, I personally have took Postinor2 few times and almost each time I get a different reaction to it.
I had experienced having no reaction at all, having menses come immediately the next day, in a few days or in a week. I've also had experience of having period for 2 straight week continuously. I've asked pharmacist and gynaes about this and they have all assured me before that it's normal and every person reacts to it differently.

So rest your mind and don't worry too much. This kinda thing works properly most of the time.

Yes it did work every single time. If not I'll be pregnant already by now no? 

Just get a pregnancy test kit and test. Settle.

Btw, did you follow the instructions given on the box in the first place?

Try providing more info like when was her last period, when did you two had intercourse, when did she eat the pills, how long is her menstrual cycle, is her cycle usually stable or not, is this the first time she had sex, did she eat anything wrong, did she change her eating habit, is she under any stress (work, study, family, etc.). Some of these stuff are not easily seen or observe but it doesn't mean that it's not there, especially stress.

The bolded part just shows that you have nothing much to worry about, and we can't really help you with the dates anymore.

What you have to do now is buy her a pregnancy test kit (around RM10 or so) and ask her to test it first thing in the morning.
Just relax and don't worry. She's probably just stressed over studying again plus the stress from the efficiency of ECP, which makes it even harder for her menses to come. I had a friend who miss three months of period due to stress, that just shows how effective stress is in delaying period.

If she's pregnant and she is having period (or bleeding a lot), it's a major problem already and may pose serious threats to the growing baby inside.
So yea, what do you thing?

You don't sound serious about getting her a simple pregnancy test, how long has it been already since you guys started worrying?