You're going to have to grow ALL of them at least to sexual maturity to keep the healthiest female. You don't even know which is the gurly until then. Read the link in my siggy, and the 'continuous canopy' sticky in basic that explains about plant spacing at different ages. FINISHING 1-3 plants in that space is correct, but you know that you have to start at least 4 to give the best chances of a healthy female, and even then, it is not 100% guaranteed.

Can I at least slap 'ya around a little?