<GULP> I can't advise you on this. Is there any way to see a photo? If it is fungal, it might be a good idea. If it is just a case of sunburn, the leaves if green are still capable of providing energy to the plant. Its a tough call. I'd hate to say cut it, and then have you lose it. One thing you could do is take a few of the leaves, and start some leaf cuttings. I think that the leaves would bud even if sunburned. Leaf cuttings are always a good insurance policy.
Tell you what. You do as you feel it. If you lose the plant, I can replace it for the cost of shipping which is 3.85 (assuming you are in the USA) Maybe you can try the trimming of the rosette experiement, and let us all know the results. This would be good information to have. I believe the plant would return from the roots. The South Africans can take a lot of abuse. I froze my pot of D. aliciae solid last winter. The rosettes withered and turned brown. By spring, new growth had already begun from the side of the rosette, and the plants now look better than they did when they froze. This was also the case with my D. regia. Many of the other South African species also have a periodic rest where the rosettes become ratty looking and wither. With slightly less wet conditions (just moist) and good air circulation they recover and begin their cycle of growth again. This often happens just after flowering. I think a seasonal rest, although not strictly required, really helps maintain the vigor of these Drosera species. They are built to take it, and as such, we should give it to them.