yea you can top her, i usually top when the 4-6th node is well developed, but you should be cool. i have even topped a few plants with less nodes then yours.
The plant can be topped at this size it will stop the verticle growth for a while but it will give the plant a chance to get the side node's to get some size.I always would advice topping a plant during the early growth this will make the plant produce two top's.Then in the second week of flowering if these two top's are then topped again this will give you 4 cola's.I have messed around with topping of plants for some time a few years back and it can be topped dureing veg then let the two top's get big enouth to top again then top them again when in flower.This will then give you the first set that you topped insided by another two all togeather giveing you 8 cola's.But i have gone back to the old method of topping during the first week of flowering just for the two main cola's.And i am not 100% convinced that the topping of a plant during flowering give's you that much more weight than a plant left to run the normal course.I like to see the one main trophy bud.But for produceing a mother that will produce more clone's cloneing during veg is def the way to go.