Image Size Issue - Simple for you Experts!

I am new to the Photoshop experience and have scanned several images and resized them in Photoshop (grayscale tiff's, 200dpi, resampled, no compression). When I open or print these images, they look great. However, when I share these images via Email with a co-worker, the images come up as a different size (much larger) when she opens them with her install of Photoshop.

What am I doing wrong?

Thanks!

What am I doing wrong?

Probably, nothing. If your screen resolution is set at, say, 1024 x 768 and you save an image that's 500 pixels wide, it'll occupy about 1/2 the width of your screen. If you send it to someone whose screen rez. is set at 800 x 600, it'll occupy 5/8 of their screen width. If the recipient's rez. is 640 x 480, the image will be almost 80% of the screen width.
It might be worth asking the recipient about their screen resolution. Then you can size the image accordingly before sending it.

A good resource for scanning, pixels, resolution and related info is: <http://www.scantips.com/>
A few minutes at that site will clear up a lot of questions.

Gary