When she saves the document to send to the professor, which format is she saving it in? If she saves it as the default .odt, Word won't be able to open it. In the small window by "Save as Type" she needs to click the arrow to cause the drop down menu to come up, then select the proper Word version to save it as. My version of Open Office has the following MS Word options:
MS Word 97/2000/XP (.doc)
MS Word 95 (.doc)
MS Word 6.0 (.doc)
There is also an XML version. The latest version of Open Office, version 3, is also compatible with MS Word 2007; however, I don't know how that appears in the drop down menu as I don't yet have that version of Open Office.
Once she has chosen the proper Word format, then she needs to save the document. This is the version she should submit to the professor.