If you top the main then two shoots grow from the sides of where you topped (Assuming this is a seedling). You can top these two shoots when they have gained another node or two. Topping the main should cause lower side shoots to rise up and these can also be topped a few times. You'll end up with a bushy round plant.
Maybe better than that is to wait until she has 5 nodes then tie down the main (LST). When lower side shoots rise up then you can tie those down also. This will likely give you the same result as topping, but may take less time to veg. Alternatively do the LST and wait until you have a fair amount of shoots and a nice round plant then top once.
Mainlining is pretty fun, but it really takes a long time to veg this way.