Sunflower68, leave to remain will be granted if kevshakry meets the requirement of the immigration rules.
http://www.ind.homeoffice.gov.uk/lawandpolicy/ immigrationrules/part8
She can apply for leave as an unmarried partner, and amongst other things would have to provide proof that the relationship is genuine and subsisting.
She can also get married and then apply for leave to remain as a married partner, but would also have to provide proof of the relationship. As there are so many marriages of convenience these days the decision maker will almost disregard the marriage certificate and instead look at the other proof provided. So really the marriage will only affect which section she applies under.
Hope that makes sense.