I wonder how long they had the baby carrier. And how many hikes they had done with the carrier?
My experience with baby carriers, is that the older the baby, the less time they are content in the carrier. The baby is reported as "one year old". Big difference between 12 months and 22 months. I wonder how old she was? Sleeping, okay, half an hour, okay...then, they want to get down, walk. Fussing starts.
Just my personal experience with hiking and kids. Which is why, we kept trips extremely short. And family friendly areas, where a toddler could walk a bit. Nothing steep.