We don't know what your friend has. We can't tell you if the ones I listed are lighter.
.
My sister does not know what kind she had. In fact, she doesn't even know where it is because it was too heavy for her to use also.
However, the light weight one was from Just for Us Smokers, which is no longer in business. Their webpage is still up but, and I've tried contacting them to no avail. According to their website, their product "feature(s) a cartomizer, which is an atomizer and cartridge that is combined together. This new technology eliminates many of the frustrations users have found with dealing with external atomizers, such as clogging, wearing down, and breakage." Perhaps that is the reason that it is so light? From what research I've done, this doesn't seem like an unusual feature. Do you think that the 510 compares?
Thank you so much for all of your help!