Bismihi ta'ala
In general our esteemed Maraji' permit a female who meets the shar'i requirement of being a balighah rashidah, to marry without a need of a guardian's consent, as long as the condition of her being so is correctly defined and understood.
It is not just a matter of maturity, but that she has absolute independence in her affairs, not just financial, but social as well. And that she is completely consciously aware of what is good and what is bad for her, and is competent in her decision making.
And Allah knows best