Hello and welcome to the forum mickeylonster.
Your present income is sufficient for her application to be successful without the recourse to public fund thinghy in mind.
Dont know the exact minima but I was in the same boat as you when Wan applied and her application was successful.
One of the professional bods on here can be completely accurate with the small print and the pros and cons but in the meantime I think that you will be OK
Regards harvey & Wan