It's very tempting to lose weight using drastic methods but those don't tend to stick unless you're able to find a plan that will work for a life time. I haven't been able to find that, but I'm working on it.
In the meantime, I would definitely use greek yogurt as a base for your smoothie instead of water, to up the protein and calcium at least.
I admire your motivation and I do think green smoothies can add some great nutrition to your daily intake, but having some balanced meals would be more ideal. Perhaps you'd be willing to have your green smoothie for breakfast and then have two healthy meals the rest of the day? Just a thought.
I wish you great success and health.