Just to avoid any confusion.
My point is that your wife stand to lose out by leaving at the wrong time.
If she want to be granted British Citizenship she should not up sticks and leave after just forking out money for the ILR.
1. If you remain out of UK for 2 years or more the ILR of your wife will no longer be valid. She return legally and will have no eligibility to enter UK without a new visa.
2. If your wife has ILR and you leave UK for 1 year she will not quality for British Citizenship when you expect her to due to UK residency requirements
The residency requirements for British Citizenship are:-
- you have not spent more than 270 days outside the United Kingdom during the previous three-year period
and
- you have not spent more than 90 days outside the United Kingdom in the last 12 months of the three-year period.
There are some allowances and exceptions accepted. But not so much.
Just be sure to understand the implications of leaving UK for lengthy periods