So probably not conceived on Demonreach. That would have been, at a minimum, a 15 month term.
Assuming Georgia stayed human the whole term, I think we're looking at a 9-month pregnancy +/- a bit. The longest human pregnancy ever recorded was 12 months (and it was quite an outlier; so much so that (despite multiple doctors attesting it) there was claim of a hoax).
Wolves' gestation is even shorter -- typically 2-2.5 months.
I don't think 15 months is realistic, sorry.
Of course, Jim may write it that way anyhow. We know (from some of the "impossibilities" uncovered in the timeline) that Jim's a bit prone to working from memory and going "that's probably close enough."