I suppose it is possible, but it would depend on your starting point (I.e. Pitch, resonance, speech patterns, etc.) and the voice training method you use (there are several methods available online, and you can seek out a speech therapist in your area that works with trans women, and some speech therapists offer Skype sessions), however the average amount of time to develop a natural sounding female voice is several months to a few years; one reason is that voice training puts a lot of stress on your vocal chords in the beginning.