Is buying a gold ornament with "Rejoice, for you are victorious" written on it considered a violation of creed or a talisman, especially with the existence of weak sayings that it was inscribed on the Seal of Prophethood?

It has not been established that the phrase "Muhammad is the Messenger of Allah" was inscribed on the Seal of Prophethood, and whatever has been reported regarding this is not authentic. Buying ornaments is permissible for women, provided the intention behind wearing them is not to believe that they bring benefit or victory. If that is the case, then it is not permissible and is considered among the forbidden amulets (tama'im), which constitute minor shirk, whether they are from the Qur'an or otherwise.