A few notes:
As much as I want to push people to use systems other than Microsoft Office (importantly, systems that use an open file format, so that it can be used in the future easily), there are still advantages to using Microsoft Office.
How much complicated stuff will she be doing with Office, or will she just be using it like most people, to type up reports or essays, and perhaps the odd graph from a few numbers in a spreadsheet? OpenOffice can capably do about 90% of what Microsoft Office can do, and since most people using nothing like this amount, it suffices. There are some that will use the more unusual features of Microsoft Office though, and have issues with anything else.
File formats: OpenOffice can save as .odt (Open Document Text), or various Microsoft Word formats (the Word lookalike, this is). The former is better because it's easy for others to write another program that can open these files, as its format is openly documented (and thus, if OpenOffice goes belly-up, you can still open your documents in years to come).
The later is better to share information with. At some point in the future, this may also include .docx formats (for the latest versions of Microsoft Word). Keep saving to 'Word 2000/97 format', as this is the most compatible for technical reasons.
Finally, some Word files do open strangely in OpenOffice, but the number of these now is rare, and being reduced with each update.
PS. If you do want Word, then as a student (I assume your wife will classify as one, while on the course?), Microsoft sell the complete Office package for £40. This is far less than their regular retail price. I think you need to ask the department or institution she's studying with for more (it's an offer I've seen through my uni department).