Using multiple accounts in single file

[Matthew]

Hi

I am relatively new so am trying to understand some of the concepts.

I have created a single Gnucash file for my household accounts.  So this
includes my personal account, my wife's personal account and our joint
account.

I want to produce a report which shows the income / expenditure for my
wife's account only.  However, the report I use will show combined
Expense accounts (ie those which are written to by other accounts).

For example 'Expenses:Food': both my personal account and my wife's
personal account have recorded expenses against 'Expenses:Food', so how
do I separate only the expenditure by my wife in this category?  I guess
it cannot be done without separate Expense accounts, which indicates
that perhaps I should use a different File altogether, instead of trying
to combine multiple accounts into one file.  What is the best practice?

Regards

Matt