Section 526 applies to servicepersons and their debt. In this case the serviceperson has no debt with you.
However, you may want to look at this from a PR stand point, especially if your borrower relies solely on her husbands income. Although, IMO, you are under no obligation to reduce the rate under the Act, this may be the opportunity to build "goodwill" with this customer and within your community. How would it sound if this went to press. Even though you may be within your rights under the ACT, you would still be the big bad bank.
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The opinions expressed are mine and they are not to be taken as legal advice.