I figured it out!
While thinking random things I realized something for my Hetalia X Fem Scientist Reader they all are have mental issues and/or Genetic issues
Katya Cant control her anger or streagth
Sayuri Is A has a disease where your body ages slower than normal. and Osteoporosis
Reader has the mentality that she can do something no one else can and I'm better. She will do what ever it takes to come out on top