Lycaon - Saturday, April 21st, 2012 - 8:42 AM
You could also say that the effect of your sister getting a bit better could be your own desire for the blessing to have the intended effect. The act of the ritual itself increased the desire and belief that she would be better, with you, and your other family members.
Just looking at it from all sides makes you know that there are multiple ways you can take the whole business. Some people believe that force of will alone is enough to make change take effect in the real world. Maybe this is a variation upon that theme.