Once she's old enough for alternating internodes, it's too late for topping.
Using a stake and some twist-ties, you can bend the growing tip down as far as it it seems possible without damage. This promotes side-branching. Not quite the same as topping, but usually fills in nicely.

Carefully bend her top down to a level below the rest of the plant. (bamboo stake and twist ties) This promotes side branching which will give some pretty good secondary (non-cola) buds. Takes half a day or so after tying her down, but the growing tip will eventually turn itself 'up' to the light. Ease-up (light breeze) with the fans for a couple of days till the stalk strengthens.

You can do a search for the LSTTT technique (Low Stress Twisty Tie Training, I think)

Also...make sure the clones are well rooted before attempting this. :jointsmile: