It's very sad that it happened. However, I will say that Farmville, World of Warcraft, Cafe World, Assassins Creed and a myriad of many other games can be addictive. I'm as susceptible to spending too much time playing games and having no life as anyone else is. We can't really blame anyone but ourselves for setting in front of the computer and zoning out to real life.
I think we've done it to ourselves because it was easy entertainment for our kids and we excused it as "well at least I know they are home staying out of trouble and they are safe"... Addiction whether computer based, physical, mental or any other form is something that we all need to guard ourselves against.
There is no excuse for what she did only an example of what we are allowing ourselves to become because there are less or no risks in a virtual world.