Doesn't the statement actually have to be defamatory to be sued for? (Ie lower someone's estimation in the eyes of right minded people" -case was someone accusing someone of reporting a faulty gambling machine -most normal people would think that a good thing to report. Therefore accusing someone of "grassing" isn't defamation.
Here if it's claimed she is an only child, that defames no one. We just think she is bending the truth. Not that Samantha is lying about her parentage.
On that basis there is no case.