I don't think there is a "set" time. However, I think the time needed is subjective. You need to be sure YOU are ready, you've checked all the baggage you can, and you are emotionally prepared to give a woman what she needs. This lady you speak of that you are seeing, had been on her own foe 12 years..that is a long time to get used to your independence. A long time to be quite cozy in your own skin, and also used to your space and freedom...it is a lot to give up. You need to allow her time to adjust, to invite you into her space, as she does you, as well. It sounds like she has been jilted before, and as the saying goes..once bitten, twice shy...if you care as much as you say you do, then be patient. I think that is all she is asking...patience and understanding. We don't expect perfection..but from one wounded soul to another...after 12 years, I would be gun shy as well. Men need to understand the power they have. You have the ability to change us and the world we have built for ourselves... we can change from being like Beyonce..and independent woman, to your loyal wife, and realistically as much as we int about about " I wont let a man change one!" everybody has to give up something to gain, and in relationships, that can be our independence & freedom and we have to be ready for that as much as you have to be ready for a a committed relationship.
So be patient, be understanding and she will learn to trust that you are the man you say you are.
" Nothing easy is ever worth it"