You have given her very high resolution images.

People are extremely confused about PPI vs dpi. The PPI is INPUT resolution to a printer driver. The dpi is the OUTPUT resolution from a scanner or a printer.

PPI means, "How many original, created in the camera or from a raw file in post processing pixels am I going to spread over each inch of printed or displayed output?

'dpi' means, "How many scan cells am I recording per original inch of scanned copy?" (The result is stored as pixels in a file!). 'dpi' also means, "How many fine dots of various colors and sizes do I need to print to reproduce each pixel in this image file?

Every JPEG file or TIFF file has an EXIF table that contains a figure for DPI height and DPI width or X resolution and Y resolution. These values can be set to any value. In photography, they mean nothing and say even less! But in the offset printing world, they tell page layout software how large to display an image when it is "flowed" or "placed" onto a page layout. If the resolution is 72dpi, the 4016 x 5020 PIXEL image will be HUGE — 55.78 by 69.72 inches. If the resolution is 300 dpi, it will come in at 4016/300 by 5020/300 inches, or 13.39 by 16.73 inches. But in either case, the page layout artist who understands his/her software can make it fit the space allotted for it.

In short, the dpi of a file does NOT necessarily relate to a particular size. But the dimensions of the file in PIXELS determines how large you can display an image at a particular dpi. Designers who don't understand this are a dime a dozen. They just look at the file header and see a lower number than they would like, without looking at the overall dimensions of the file and realizing it will work.

File size in MB is irrelevant, too (unless you're concerned about storage or network bandwidth), because the file type and the amount of compression applied to the image, and the type of compression used, all play a huge role in determining the file size on disk. The same 16 MegaPIXEL image might be 19.8MB as a raw data file, or 95.6MB as a 16-bit TIFF image in Adobe RGB, or 8.7MB as a 90 quality JPEG image in sRGB. Changing the resolution settings won't affect the file size or pixel dimensions!

This may help. From a Sony website:

"DPI refers to the number of printed dots contained within one inch of an image printed by a printer. PPI refers to the number of pixels contained within one inch of an image displayed on a computer monitor."

When an image has a metadata tag that says it is 240 dpi, that number is meaningless until you print. Then the interpretation is that if you printed the image at 240 dpi it would be a given size. If you print your 4016x5020 image at 240 dpi, it would be 16.73" x 20.92".

The truth is you can change that number to 4 dpi or 4000 dpi (without resampling) and it won't make a difference - since you are not changing the actual resolution, in pixels, of your image. What matters is the number of pixels in the image and not the dpi which it seems you understand quite clearly. The person stating the requirements doesn't understand. You are correct - you are providing a 20.2mp image which is not low res by any standard.

Have some fun and change the dpi number to 4096 dpi and see if their heads explode.

Another possibility is your client has corrupted the image files between receiving them from you and sending them to the people responsible for the website. Anyone saying 'DPI' is anyway related to the pixel resolution of a pixel-based digital image doesn't know what they're talking about. Apple email is a typical culprit in dynamically and unexpectedly resizing the pixel resolution of image file attachments. If possible, try to cut out the middle man and send the properly sized images to the website administration directly. Or, send your client a public link to access a download site such that the website admin can download the files directly.

Another idea is to ZIP the file(s) and resend to your client as a ZIP attachment. This does nothing to make the JPEG images 'smaller' as a file attachment. But, this approach prevents an email client program from resizing the JPEGs as they're safely enclosed 'as is' inside the ZIP container. Have your client forward the ZIP attachment to the website admin, who will receive the properly sized images when extracted from the ZIP attachment.

Open your image in PS - or whatever. Then - go to the Image settings (not Canvas). I'll bet your photo is showing like 42" on the horizontal or vertical image size. Uncheck the 'resample' box so that the aspect ratio and DPI are preserved. Then reduce your image size to 4"x6" or whatever. Your DPI will probably jump up to 800 or more. Then save it and send them the updated file. I believe John Swanda has it right - your recipients need to be educated - as they should be able to perform the above operations on their own computer.

The Adobe software does not use the camera settings like picture style, or Active-D, nor sharpening, nor noise reduction. The Nikon software does when displaying the image as these in-camera settings will be applied to the saved / export version of the RAW. As compared to LR Classic, the most obvious visual difference is that Adobe defaults to a 'picture style' = Adobe Standard. If you'd go into the camera calibration section (Develop module) after a NEF import to LR and change the profile to Camera Standard, you'll immediately get closer to the colors and saturation of Nikon (or Canon, Sony, etc) for their 'standard' profiles.