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You will have to apply spouse visa for her as spouse of British National.
For spouse visa, you will have to show that you are earning £18600 per year.
A holiday visa can not be switched into spouse visa with in the UK. She will have to apply spouse visa from her home country.
If you can prove that you have been living together for 2 years together out of the UK then she will be eligible to apply ILr ( Indefinite Leave to remain ) after spending 3 years in UK.
If you can not provide living proves out of the UK for 2 years then she will be eligible to apply ILR after living 5 years in UK.
After ILR, she can apply British Naturalisation and Passport.
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