Is a person predestined or free to choose a spouse, and should a girl agree to marry someone who doesn't possess all the desired qualities, fearing delayed marriage, or should she wait for a righteous spouse?

Humans are both predestined and given free will. They are predestined because their actions do not fall outside the power and will of Allah. They are given free will because Allah has granted them the ability and will to distinguish between good and evil. To address spinsterhood, one should strive to marry a man of religious devotion and good character, for the Prophet, peace and blessings be upon him, said: "If someone whose religious commitment and character you approve comes to you seeking marriage, then marry him. If you do not do so, there will be tribulation on earth and widespread corruption." One must be cautious not to rush into a choice, for the fundamental factors in accepting a husband are religious devotion and character, followed by lineage, wealth, and beauty. If Allah knows the sincerity of a girl in seeking a righteous husband, He will facilitate that for her.