Wait actually, having reread - it sounds like that initial stage was fine, but after you’ve declared your income you’ve now got the email. It is only your household income that they count so I would call them.
When she did her application online, they should have asked the contact details (email) of the person or people supporting her application. They decide the maintenance loan on the basis of household income just like normal. Did she put down her mother and father by mistake on the drop down list of the people in the household supporting the application?
Have the rules on household income changed this year?
My step daughter has just had an e-mail from student finance which specifically asks for her Mum and Dad's details. She has always given mine and her Dad's details (and not her Mum's) and we have both declared our individual incomes as she has always been resident with us. My partner and I have done the same for my son and his Dad has not been involved either.
So have the rules changed so that "parental" income is now used or is the wording just confusing but they still mean "household" income?