Thanks for your question. I will try to help.
I think you have misunderstood the requirements at some point.
As she obtained her first spouse visa after 9 July 2002, she must complete 5 years residence in the UK before applying for “indefinite leave to remain” (it was previously just 2 years.
So, she can only apply for indefinite leave to remain once she has been on her spouse visa for 5 years. Before her visa will run out before she reaches this point, she must apply to extend it (all persons on spouse visas after 9 July 2012 have to).
The Life in the UK test is that test that you have to pass in order to be eligible for indefinite leave to remain. She is not required to pass this test to simply extend her visa, which is what she must do in October before her current visa expires.
She will extend her visa for a further 3 years, which will bring her up to 5 years total in the UK. Once she reaches 5 years she can apply for indefinite leave to remain provided that she has passed the life in the UK test at this point.
So, she has a considerable period of time until she needs the life in the UK test and should be able to extend her spouse visas relatively easily.
When she applied for her original spouse visa she would have had to show her knowledge of English test results (otherwise she would not have received her visa) so I would just check that the test she passed does not have a validity expiry date. If it does then she would have to take a further English language test but I presume this is not a problem since she would have had to passed it in 2014 when she applied for her original spouse visa.
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