The cacti is located at the tip of the balcony, it receives around 4 hours of sun daily.
Here's a picture of the plant and her lovely pupping.
The pic is around a week old, the lil' girl has become a lot bigger now!
How about doing damage to the cacti? although even if it works, I might not consider doing it, because I will feel like a tyrant slave-holder then.
Regarding the energy required for growth:
Sometimes a lot of energy is available in a project, but fewer than needed manpower makes it to go slow.
Imagine you're building a house.
You've bought all of the materials, but you only got 1 builder, obviously the more builders you have here, the sooner your house will be ready.
The "builder" in that analogy is comparable to the "growing tip cells" of the pupping.
They can only divide at a fixed rate, no matter if there's so much excess energy/nutrients available, cell replication is so complex and takes some time.