In reply to TheDrunkenBakers:
If she is at school you should be able to get cheap educational versions of MS software. In addition check with your IT bods if there is a staff program available. Not sure exactly what criteria is used but MS do have a scheme where they offer very cheap copies to employees of some companies (think the install for my mac was about a tenner).
Going for open source. Libre Office is a better choice than Open Office since it is actively developed.
Open Office was first and was supported by Sun who amongst other things owned the name etc. However it was primarily developed by the community.
Oracle then brought Sun and managed to piss off said community in various ways. This resulted in the project being forked and LibreOffice which had the majority of the devs etc joining it.
After staggering along for a bit Oracle gave Open Office to Apache but the damage seems to have been pretty much done.