daviamp, Her body has no way of knowing where she is in her monthly cycle when she takes pills. If she stops her pills, she will bleed. This is called withdrawal bleeding when the pill's hormones withdraw from her system.
This is why her inactive week of pills contains no hormones. It will make her bleed and she will be assured that she is not pregnant (so she does not have to worry constantly that she is pregnant). Of course when she does not take the pills, her body does not know if she is on her inactive pills or if she stopped taking it and viola - a period when she does not want one.
You should explain the importance of taking her pills to her, as well as the risks of making a baby when you are not ready for it. Try to get her to fit it into her daily schedule, so she should take it with something she does every day - like brushing her teeth, or eating dinner, or dressing, or going to bed. Some smart phones also have apps to remind her to take her pill.
Checking up on her is a good thing until she can prove that she is taking it regularly. You can always check her pills before sex (or ask her about taking it) and use a condom if she did not. This is especially important if she is under stress or traveling and might not take it as she should.
Best of luck!