Hi,
Your wife is correct, in terms of her bank interest, in addition to the starters rate for savings of £5000, she would also be entitled to the £1000 Personal Savings Allowance, as well as any unused Personal Allowances.
To confirm why her tax code has been reduced for both years, we would need to review her record and so she will need to contact our Income Tax team.
Income Tax: general enquiries
Thank you.