Could my girlfriend be pregnant?

It is not normal to miss your period for several months, except when you are taking certain contraceptives, which can be bad for your health. If your missed periods continue, see a doctor.

 

I think that her family sounds like they genuinely care about her, her health, and well-being a hell of a lot more than you obviously do, or she'd never be in this position.
I also think that if you're that goddamned ignorant of basic human physiology you should be gelded and not allowed to breed.

We all have an immutable responsibility to our lovers, which on the most basic and fundamental level is to ensure their safety and protect them from harm, whether that be from STD's (if you don't know, look it the fuck up), unintended pregnancy, damage to established relationships, degradation of their self-esteem and sense of self worth, or financial, reputational, professional, or educational harm. In our patriarchal and puritanical society, women are the most vulnerable to the often brutal consequences of all of the above, and what you describe is an inexcusable, abject failure to fulfill your most basic duty as a man, a lover, and as a human being on a truly colossal, and quite possibly for her, catastrophic scale. This is the 21st Century; the "Information Age". All of the collective knowledge and wisdom of humanity is there at your fingertips. There's absolutely no excuse in this day and age for this shocking level of stupidity.

A Google search of "effectiveness of coitus interruptus" returned 81,300 results in less than a second.
There; I did part of your homework for you.

Birth Control Methods & Options | Types of Birth Control

Prevention - STD Information from CDC

 

my first wife was like that. she went on the pill at 12=13 to regulate it