Okay, I know how to do some of this on a Windows machine, but I'm not great with the Mac.

A family friend just recently found that her entire iPhoto library had been deleted. Apparently she was adding some photos from a GMail message and got some sort of notice that she should rename her library. After doing some other things (I'm getting a vague recount here), she soon found that everything was gone. Naturally, she's distraught because she had four years of photos of her very young daughters on there. She was using Time Machine but when she called Apple support for help, they went in and looked and found that Time Machine was - for some unknown reason - not backing up her photos.

So that's where we are. What can I do to help her? I've been trying to use this program called "Disk Drill," but while that seems to be finding some files, they don't seem to be ones inside the library, but ones that were brought over from an old computer and others taken with cell phones that got put onto her computer somehow.

I currently have the drive out of her MacBook and hooked up to my MacBook (so as not to write over anything). Any help would be GREATLY appreciated.

1. Look in her Time Machine for the photos. Time Machine backs up everything that is not purposefully excluded. Keep going back through dates.

2. Where were the photos ORIGINALLY? AFAIK, iPhoto imports copies.

I wonder what that dialog was. First thing is to try and find where the library went.

The normal one is in a Pictures folder inside the user account. Look for anything iPhoto related there. Perhaps the user held Option while launching it, which lets you create a new library under a different name or location. http://support.apple.com/kb/HT1229 has some info on this and how to move a library.

If you have found the library, and are sure iPhoto is pointed at the right one via option, but photos don't appear, it may be a database issue. In Finder, open the iPhoto folder. (For newer versions, hold control and pick "Show Package Contents" to open.) Look for the original photos in the file structure, possibly in folders named Masters or Originals. If they are still there, it is a DB problem. Refer to this: http://support.apple.com/kb/HT2638

The Time Machine comment is a bit odd, since as Bruno said, it backs up everything by default. Well, unless the user moved the iPhoto library/created a new one out on the same drive as the Time Machine backups. Open Time Machine in System Preferences and look at the settings to see if anything is excluded.