If your friend tries to increase the size of the image beyond 100% its actual size its just going to blur. Thats just a fact of digital images and true regardless of what program its made from.
The best solution is to render at the maximum possible size that DAZ Studio will allow which is 10,000 x 10,000 pixels. However, that is going to take a longer time to render and will create a much larger file size. On the bright side, your friend will be able to see the extra detail. She will have to zoom out though to see the whole thing. The largest I have rendered is 6400 x 4800. That was more then enought to see details in the image.
To give you a quick rundown on some of your advanced render settings:
Bucket Size: This is how many pixels squared that the computer will render at one time per CPU core. 32, which is the middle setting would mean that an area that is 32 pixels by 32 pixels is processed by the CPU and then moves to the next area that is 32pixels by 32 pixels.
Raytraced Depth: This effects reflections. If you dont have any, leave it at two. If you do, then this value tells the computer how many times an item can reflect back and forth between two reflective objects. Think of standing between two mirrors and looking into one, you see infinite reflections. In DS however, the maximum number of reflections you would see is controled by this value. maximum is 16.
Pixel Samples: In short, its the secondary quality settings. For test renders keep the value low. For final renders you can set it higher. Higher values will help give a more natural look when using Depth of Field.
Shadow Samples: This determines the quality of your shadows.
Gain & Gamma: I leave mine at 1
Sahding Rate: Your primary quality control. Lower values mean much crisper images. default is 0.2 For test renders of complex scenes you would want to set this up to 0.5 or even 1 to render faster. But for final images, if you want a crisper image, set it to 0.2. Mixed with a high Pixel sample and Shadow sample rate can increae render times but help produce crisper image.
Here is a link to the more technical explination: http://www.k-3d.org/wiki/RenderMan_Controls
My advanced render settings screen shot from DS3
Click thumbnail to see full-size image