Thanks for your question. I will try to help.
The safest way forward would be to wait until March 2017 and then apply for naturalisation.
Once you are married she will obviously be married to a UK citizen. This means that the spouse requirements for naturalisation apply, which are here:
You will see that part of the requirements are that she must have lived in the UK for 3 years before she applies AND that she must not have broken any immigration laws whilst in the UK.
So, given that she received ILR in March 2014 you can be certain from this date that no home office caseworker could claim a breach of immigration rules as from this date.
Therefore the most certain and least controversial way forward would be to wait until March 2017 when 3 years have passed from when she received ILR and then apply for naturalisation.
The fee to naturalise is very expensive (£1236 at the moment) and so I would strongly suggest that you instruct a solicitor to prepare the application for you to check that there is nothing missing from your supporting documentation.
Once the naturalisation application has been approved she will receive a certificate of naturalisation. She can then attend a citizenship ceremony and after this apply for a UK passport.
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