She needs to see a doctor--we are not qualified to give medical advice. There are several reasons why this could be happening, though. She could be pregnant, even if you think you have been as careful as possible, and used birth control every time. There is a failure rate for each type of birth control method. Another reason could be if she is very thin, and exercises a lot. If a woman's body fat percentage is below a certain level, it can affect her periods. That said, she needs to get to a doctor, even if only to set her mind, and yours, at ease. If she is also a college student, she can go to the health service.
I would never be so bold as to try and come up with a diagosis. I also agree that she needs to see a physician. Menstrual cycles fluctuate from female to female. While some females have regular monthly periods others do not. She could have an underlying medical cause or be one of the people with irregular periods. In addition, the dizzy spells she is experiencing may be relative to not having had a menstrual cycle or they may not. The best advice that I can give you is not to try and get medical advice from a layman. Even a physician could not diagnosis her issues without running tests or at the least talking with her.
Good luck and I hope she feels better.
Anxiety can cause a girl to miss her period. If you are dizzy or feeling lightheaded it could be that you is making yourself sick. Panic attacks mimic feeling like you are having a heart attack, with symptoms like a tight chest, sweating, dry mouth, dizziness and stomach pain.
If you visit an ENT, they may notice nasal glands that are dilated, which connect to your Eustachian Tube in the ear. If the crystals in your ears, are unequal then you will feel off balance until that problem is solved. (The doctor can carefully manipulate your head to balance out the crystals)
Also, a condition called positional dizziness, can happen by moving your head too quickly when bending or turning. This could start from a simple jolt or sudden jerk without you even realizing what you did. By simply paying attention to how you move, and not jumping up or down suddenly, can improve symptoms.
This feeling is hopefully temporary and will pass as you try different doctors or treatments. Our bodies are very capable of bouncing back and you can get well with time and patience.
Funny....I did not discuss such things with my "boyfriend" at that age. BUT....since you asked the question common sense is go to the doctor. If you personally know why she has missed her ..... then in about 6-7 months it's possible you both should get ready for that little bundle of joy! Either way...she has got to go to the Dr! Blessings....jm