I can tell you that if you ask them the answer will ALWAYS be NO. My almost 4 year daughter still says NO when I ask her if she has to go potty and she has been "potty trained" for 1 1/2 years. I agree with your husband that it should be started because kids do grow out of the cpacaity and sizing of diapers and that seems more cruel.
Set a routine and STICK WITH IT. Kids always have set-backs and periods of disinterest but you have to stay stearn and stick with it. In the long run everyone will be happy. It does not have to be forceful but rather routine. Read books, look at puzzles, listen to music etc. while she sits on the potty. She does not have to go every time but it establishes a pattern for them recognize that they will be doing this quite frequently throughout the day to make sure they do not have accidents. Pull ups help as it makes it easy fo rthem to learn how to pull their pants up and down. Practice good hand washing...start small. Get the basics of the process then work on the act itself.