Zero - she delegates it to her husband. (duh)
I am no energy expert, but I do know that using compact fluorescent bulbs can save tons of energy and lots of money! The US government's Energy Star website notes that the bulbs last an average of 10 times longer than traditional "Edison" bulbs. They also generate 75% less heat which means they are safer and waste less energy.
Since I last changed (via delegation) a lightbulb, I learned that our precious CFL's contain a very small amount of mercury, about 5 milligrams, or one-one hundredth (1/100) of that in a standard thermometer. No mercury is released while the bulb is intact and in use. Technological advances will soon lessen and possibly even eliminate the use of mercury completely in CFL's. So while the bulbs pose no apparent threat while functional, it is not a good idea to blithely toss them into the regular trash where the will eventually be crushed. It is best to contact your local solid waste management department. Most will either make an appointment to pick up the product or provide information regarding where it can be disposed of properly. Many states have only a few recycling posts, but the local agencies can safely transport them to the correct facility.
In closing, if you are worried about the mercury level in Compact Fluorescent Lights (CFLs) please consider that it would take 100 bulbs to equal the mercury content in one of the old standard thermometers our mothers and pediatricians inserted under or tongues (or worse) when we were young. Wouldn't you much rather have a lightbulb above your sink than that? Especially if changing one bulb can save you up to $66?