Hello from JustAnswer.
There is always a chance that she could be pregnant, but the likelihood would be very low.
A condom is not perfect at preventing pregnancy
, but it is still good.
If pregnancy does occur, it will typically cause a missed or late period. Some women can have some early bleeding associated with implantation of the pregnancy, but that would be expected to be about one week before the period.
In addition, if the period is two weeks early, that would indicate that the sexual encounter occurred three weeks before the anticipated period, and this would typically not be a day on which the woman is very fertile.
The fact that she is nauseated is a very non-specific sign of pregnancy. Certainly, many pregnant women are nauseated, but there are many other common causes of nausea
So, while pregnancy is always a possibility until a test shows that she is not pregnant, the likelihood is quite low.
If I can provide any further information, please let me know.