First, let me congratulate you on surviving breast cancer. Second, any woman with a history of cancer should certainly consult her doctor before planning a pregnancy. Third, no medical decision should be made on the basis of a news article, although such articles can be very useful in providing information that can be discussed with one's doctor. Presumably, women with such tumors were included in the study group. Even so, the women who became pregnant had a better prognosis.
Similar findings come from earlier studies in Europe.
As the story points out, this may be because the women who became pregnant were healthier. It is important to note that this study looked at the statistics for a group of women. Statistics tell what is likely to happen in a group of women. They say nothing at all about what will happen to an individual, such as your friend who relapsed shortly after becoming pregnant. In any case, much more research is needed on this topic before any recommendations can be made to individual women.