No she won't automatically be granted as you are married, she would need to apply for further leave to remain in the UK as a spouse. If her au pair visa was for more than 6 months she can apply to "switch" from an au pair to a spouse visa. (Someone with a visa of less than 6 months cannot switch and would have to go back home to get a visa to come back to the UK). This spouse visa will be for 2 years and will allow her to work, and after the 2 years she can apply for indefinite leave to remain. She must apply for the spouse visa before her au pair visa expires otherwise she could be deported.
The application could take months if submitted by post (although I think you can go in person and get it done the same day) and in the meantime she will only be able to work as the au pair for the family she originally worked for. The other option is to go back to Turkey to get the visa there. It won't take as long, and you can have a holiday while you are there. It also costs less. The rules are just the same as applying in-country so she won't be any worse off.
Hope that helps.