As mentioned prior, the pregnancy story was likely the only way she could alert to the ongoing abuse. I don’t know if part of the intake, or continued care, in the juvenile facility would include a pregnancy test.
Her parents would likely have been able to get her medical reports or records. Assuming they cared to but it sounds like they didn’t, from what we know. JMO
A female can ovulate up to 2 years prior to beginning her actual menses. So it was possible that she was pregnant. Altho back then, a sonogram may not have been available until 16-20 weeks gestation. JMO