If I recall correctly, Microsoft has never updated MSN Explorer for the Mac since its original release.
This is a shame, because the updated Tasman engine it uses is one of the Mac's best-kept secrets. Although its speed is lacking, the upgrade to its standards support blows anything out there, even Mozilla, out of the water. Of course, no one uses it, since you have to pay up front before even trying it out. I don't use it either. End result: nobody knows about it.
Shove Firefox at her and let her discover what Web browsing can be. I'm sorry to be so blunt, but it's doubtful that MSN/Mac is ever going to see another update, so I don't see much of an alternative.