Hi, I'm sorry you're not feeling well. I wish you a speedy recovery.
Question, I'm really a bit confused, please pardon me....since you're a vegetarian (are you a new vegi?), why are you considering Slim Fast? Limiting calories, carb, sugar, fat and sodium intake and balancing nutrition within vegetarianism is quite simple. The carbs, sugars and sodium in Slim Fast are just outrageous....and it has double the calories and significantly lower amounts of protein in each can VS a single scoop whey protein shake (which is your best bet).
On a natural path (without drugs, starving yourself or surgery), it really cannot go any faster than being a calorie counting vegi (bonus for organic), being that exercise is something you are unable to do right now on a temp basis. What does your daily vegi menu look like?
There's a vegetarian forum here, you may want to take a mosey over to it for additional help.