My previous FUT surgery failed, should I do FUE now? I am a female.

I think that you are focusing on the wrong issue. First, you want to make sure that you don’t have some condition that will kill off your hair like Frontal Fibrosing Alopecia or related entities. Assuming that you do not, and you said you were disappointed with the results of your last surgery as some of the grafts failed to grow, it may be likely that the problem was with the surgical team (including the surgeon who is captain of the ship). Both FUE and FUT in the hands of experienced and well disciplined surgeons and teams, work reliably. As a female, an FUT is a better option for two reasons (1) you don’t have to shave the back of your head and (2) you had on FUT before so the surgeon can work in the same place and if there is a scar there, the surgeon can remove it at the time of the next surgery.  This time get the right surgeon to do the right job, with FUT or if you are willing to shave the back of your head, then FUE works well.