Gauss, I guess she is saving using save as, not save for web. there you can choose from 1 -12.
Sometimes, flipping (or not) an image will reduce its size bur to the patters that would compress better. Try to make a square image with horizontal lines in gif , save it, then save a copy flipped 90 degrees with the same settings...
The image might be saved using advanced compression settings (baseline, etc...)
Adding a profile increases sometimes the image size dramatically (on the first window of the save as)
Also, If you save in PSD, you have the choice to add a flattened copy or not .
This increases the size, but will allow you to open the flattened version of the image (hold down SHift+CTRL+ALT while opening the pic) to fix the blending modes, in case the change it in some way in future versions... it will also allow faster preview in file viewers, or to open the flattenede version faster (just to show to a client, for instance)
We've seen also that hiding every layer reduces the size when you save in psd... strange, but worth trying...
I was also lucky Zipping tiffs images (instead compressing during the save process, the latter could produce unreadable zips in other programs)
