Must a girl make up for the years of fasting that her father prevented her from observing during Ramadan, claiming her physique was weak, while she believed she was capable of fasting?

What the father did is forbidden. Fasting Ramadan is an obligation upon every mature, capable Muslim. Imagining a weak physique is not an excuse for breaking the fast. The father must repent and seek forgiveness.

Your relative must make up the days of Ramadan she missed after reaching puberty, along with offering an expiation for delay, which is feeding one poor person for each day. This amounts to 750 grams of rice or staple food for each day, and it can be given to one poor person or several. Obedience to parents is not permissible in disobedience to Allah.