Regarding the question of a sunni muslim woman marrying a shia man, kindly note that those wishing to adhere to Qur’ānic principles and prophetic teachings know that marriage is only permitted to certain individuals. As a general principle, the Qur’ān dictates that a Muslim woman can only marry a Muslim man.
“And do not give (your women) in marriage to polytheist men, unless they come to believe” (Qur’ān 2:221)
Regardless of what one labels themselves to be, if one sincerely believes in all the major tenants of Islam as outlined in the Qur’an and authentic Ḥadīth, they are considered a genuine Muslim.
Some of these tenants are listed below:
And Allāh Knows Best