I get that she is a kid, but when it comes to important life changing decisions, you HAVE to explain things properly. No matter how hard it is for YOU to do, you owe it to them. You can't just push it off cus it is too trouble some, difficult, or you believe they won't understand anyway. You have to at least try. She scared her mentally and now the kid is going to have abandonment issues.
To be fair that whole trip was supper sketchy too. Based on how she acted and what she said, she could have easily dumped her off at a slave trader headquarters.