Complex sentence: The only way for her to undo the curse seems to be the Platina Tiarra which grants the wish of the wearer, only she must earn the right to the Platina Princess to wear it and there are many girls who want that right.
Split into simpler sentences: The only way for her to undo the curse seems to be the Platina Tiara which grants the wish of the wearer. However, she must earn the right to become the Platina Princess to wear it, and many girls want that right.