Your friend is partly correct, but is possibly confused about some things.
The various sugar molecules (glucose, fructose, etc), like most carbon chain molecules have a property known as chirality, and can form enantiomers - essentially mirror images. These are known as D- and L-enantiomers.
Now, sugars produced biologically are D-enantiomers, and almost all enzymes for metabolising sugars can only metabolise the D-enantiomers (although, a bacteria has been found that can metabolize L-glucose). This is because the enzymes that produce the sugars are similarly biased to produce D-enantiomers. Chiral Biological Molecules - University of Texas and How did protein amino acids get left-handed while sugars got right-handed?
Sugar molecules can be created artificially - using processes which will produce equal amounts of D- and L-enantiomers. But our bodies can't metabolise the L-enantiomers, which is how a lot of artificial sweeteners work. low-calorie sugar - NASA Spinoffs
So, artificial fructose is no worse for you then natural fructose - actually, since taste response to L-enantiomers is the same as D-enantiomer, it might be slightly better since you get the same level of sweetness, but only metabolise some of the sugars you ingest.
However, any added D-fructose (and other sugars - natural or artificial) can cause problems simply by introducing too much into our diet. There's a limit to how much sugar we can absorb - and what is not absorbed is metabolised by gut bacteria, causing bloatedness, diarrhea and other issues. L-sugars can also cause diarrhea as the body tries to expel it. Chiral Toxicology: It's the Same Thing...Only Different.
A further confusion is that there's also High Fructose Corn Syrup as a food additive - which is actually a mix of free glucose and fructose. Since glucose is the primary sugar responsible for causing insulin resistance, this may be linked to increased issues such as type 2 diabetes.
For a more complete introduction into sugars and chirality Biomolecules - Institute of Organic Chemistry, University of Zurich