I put together the sources on this a while ago
here. The TLDR short of it is there was nothing indicating they were sacrificing babies as such, because the story does not elaborate.
Here's a theory on what may have been the case.
Basically, I am not convinced the conflict was anything but a pretext to get them to stop sacrificing in order to avoid what she thought was going to be their ultimate fate, i.e. the Plenty, if they restored their civilisation fully. Secondly, as other posters have raised, if manipulation of dynamis is a core concern of hers, and she believes she had to sunder her people anyway, what difference would it even have made if they did as she bade them to?