Such resemblance are strange and rare. As you said, she was calling your child her daughter and she said that as your daughter is reincarnated. We all have freedom to believe in theories we live and these thing as you said is very much connected to DNA or gene. Genetic have a very big role to play .
Later on her life, will show if she is reincarnated or just genetically same. Such Things takes time to get unfolded . Thank you.