Oh dear. I think Aery's going to be hopelessly crushed on him. She always is on anyone who can teach her about poisons, especially someone who can teach her how to infuse them into the metal and not just dip her needles and knives into the poison (and need to retreat them every time she uses them)
As Co-GM, I find these changes to be totally acceptable for your character. I think Slenderman will approve as well.