skysooner

This is how I understand it. Once an embryo is conceived, there are hormone levels in the blood that start to rise. I believe they are called HCG levels. It is my understanding that it is very difficult if not impossible to detect these levels until the embryo has been viable for at least 14 to 17 days. For most women who ovulate in the middle of their cycle, this means they can't detect it until they have missed their last period. My wife (who is anal about stuff) was absolutely sure she was pregnant about 10 days after we had sex when we were seriously trying. Her boobs were sore, and she just knew. However the tests indicated nothing for another week (and she had several blood tests done at the doctor).

I suspect that if she is pregnant, it was not your friend that did it or she is potentially lying as mentioned above. Anything is possible as the human body is too complex to say something is definitive, but it appears to me to be very suspicious.