She can't use the files directly, but Filemaker will convert FMP 4 files to FMP 10. Chances are that not all scripts and such will work perfectly thereafter without further modification but her data should be just fine. I suggest downloading a free trial copy from Filemaker's web site. Install it and use FMP 10 to open the files. Filemaker will make converted copies of the files--leaving the originals unchanged. She can then evaluate how successfully the conversion worked.
This article: Knowledge Base #750
has some useful information on the process also.
Once she's converted the files, she's welcome to post specific questions about her files and FMP 10 here to the forum for additional assistance.