Essential program download's

well it all depends on what you are planning on using your Mac for.

For messaging there is a version of most if not every instant messaging client available for Windows. (personally for MSN I prefer to use Adium).

Flip4Mac is a good little tool for watching Windows Media Player files in Quicktime. It's not a must but if you feel she needs it than go for it. Though, again, I just use the Windows Media Player for OSX.

For media playing though, watching downloaded movies and things off of the internet or DIVX or other codecs. I found the VLC Player to be my favourite.

For anti-virus ClamXav is free and easy to use. It also won't hurt your system like some of the bigger branded anti-virus apps do.

FOr downloads, I use both Transmission (Bittorrent client) and Acquisition.

Any of these can be foudn by using Google.

 

Seek and you shall find. a.k.a Search.

Anyhoo here's a few just to be helpful.

Quicksilver
Adium
Flip4Mac
Perian
SMART Reporter (Definately get that. You won't even notice it and it'll warn you should your HD start to break down in the future)

 

Oh yeah...<a href="http://www.flip4mac.com/wmv_download.htm">Flip4Mac</a> is definitely essential. Pretty much one of the first things I download when setting up a new system. And, if you want any other capabilities for dealing with video, then the upgrade is worth the few $$. I can import and export stuff for iPod use and other things.
There are several more essentials, like Cleardock of the Unsanity haxies <a href="http://www.unsanity.com/haxies/cleardock">HERE</a>. I also use Fruit Menu and Window Shade X from them.
A good site to check out is <a href="http://osx.iusethis.com/user/antonio">iusethis.com</a>. That's actually a link to my personal profile, but you can get to their home page from there and see all the other apps with people use.
One more thing that I find handy is <a href="http://www.grapefruit.ch/iBackup/">iBackup</a>.

 

As corrected:

Please learn how to use the forum.