ask: Do anit-puff eye creams and liquids work?

I think it depends upon the individual's skin. Some medications, foods, even cosmetics can cause puffiness, as well as lack of sleep.

How long has your sister been using the product, and does she notice any difference?

I'm not sure about the Garnier product but I have combination skin and have found that Kiehl's Eye Alert works the best for me! A few other products I tried stung my eyes and skin, this one is cool and relaxing.
http://www.kiehls.com/_us/_en/face/eye-area-preparations/eye-alert.htm

One product that really works for me is Teamine Eye Complex. It helps with both puffiness and dark circles. I put it on every night and every morning and truly notice a difference. It moisturizes under your eyes, but does not feel heavy or greasy!

Another pretty traditionally remedy that works for me is simply putting a frozen spoon under reach eye on the days I seem to have more than normal puffiness. I hold it under each eye for about 2 minutes before I put my make-up on. I always keep a spoon in the freezer just in case!

I'm an Oil of Olay girl, myself, and have been since age 13. For me, the combination of their Regenerist line + at least 6 hours of sleep at night helps with the puffiness. My under eye circles are more pronounced with lack of sleep.

I like that frozen spoon idea, sounds very refreshing! A bit reminiscent of the cold cucumber slices. :))

Supposedly puffiness under the eyes is really an illusion caused by shadows as we loose volume from ageing. The only thing that really works is to build up the volume again, using an injectible like restylane. I haven't tried this myself but may do so when I need it as I age.
Creams can't really change much. They may feel nice but only the "strong stuff" really works.
I have heard that there may be increased puffiness from alcohol and sodium loaded foods. Maybe cuttng these out will help too.