The VHI payment she makes is already net of standard rate tax under Tax Relief at Source so relief has already been given whether she is a taxpayer or not and no further relief is due.
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Do check though if she is in a group scheme. If not, then it might be possible to amend her registration to a group one and thereby save 10% on the VHI premium. There are many group schemes, Credit Union etc. as an example.
However, also for 2007, as she is a non-taxpayer, if there are unreimbursed Medical Expenses then you can pay them and get tax relief on them. This is a change to the old MED scheme where there used to be a minimum excess of €125 ( now gone) and the person had to be related to you.