you can clone at any time really... however. the success rate of the clones is directly impacted by the mothers health.
why not just clip off all the rough looking growth, and leave the good stuff, and just re veg her to the size you want? its pretty much doing the same thing without having to clone.
if you read my journal... you will see that when in veg a plant can go through hell and back several times, and as long as she is healthy going into flower, work out just as good.
i had deficencies, root rot, overdoses, burning, etc, and kept her barley alive for 6 months before i straightened her out and got her healthy again. now shes about 2-3 days away from chop and looks amazing.