Image re-sizing incompatibility, CS3 v CS6??

Image resolution is stored in the TIFF XMP metadata namespace. If that is stripped out, Photoshop will use its default resolution setting.

PPI (not DPI) only matters for print anyway. Online that setting is not used.

The easiest test is to zip the files before emailing them. That way, there won't be changes made between you and her.

One thing you can check simply: send the file by another method completely different. On a memory stick, with DropBox, something.

Is the result the same?

Yes - the same - something has changed in your workflow

No - different - something has changed in your emailing (perhaps gmail itself).

7" wide at 72 dpi is a canvas that is 7x72=504px wide canvas.

2 "wide at 240 dpi is a canvas that is 2x240=480px wide canvas. So you wife image was also cropped beside having its resolution setting changed. Yoy Wife's e-male processing indeed changed her image.    CS3 and CS6 do not automatically crop images or chance their resolution

Also, check how the files get to you. Some methods, such as Whatsapp, mess with, recompress and damage JPEG files in transit.

The only thing you should take in account when posting on web is image dimensions (Width and Height) in pixels. If dimensions are the same then you can stop worrying about ppi (pixels per inch) resolution which is irrelevant when uploading to web.

However,  if something is changing things (resolution in your case) in between that can be something to worry. The way that Photoshop can change image resolution upon opening is to have script/action enabled for that job in File > Scripts > Script Events Manager.

You don't have to do that. It's a myth that web images need to be 72 ppi. PPI (not dpi) is irrelevant on the web. As long as the size in pixels is the same (her email application could cause this to change), you can use the images without changing the ppi.