waynegretzky, I have to agree with m3rma1d, your daughter will lose the weight only when she decides she can take control of her own life and the decision is hers alone.
I was only slightly overweight as a child but my mother restricted my food as early as the age of 7 for me. She constantly tried to motivate me to exercise and watch what I eat and by the time I was a teenager I really resented her for that. As a result I gained about 10 pounds every year. By the time I graduated high school I was 40 pounds overweight. Today I am 55 pounds overweight and have gained and lost the weight many times over. This is because it's an all-out obsession for me.
Now your daughter is an adult already but I am assuming she has had a weight problem for a while. I personally believe that the strongest impact you can make on her psychologically is to keep going and reach your goal. Live by example. Your vitality and your fitness will be more inspiring to her than anything you can say. When your daughter sees you and your wife slipping into smaller more stylish clothes and feeling great about yourselves she won't be able to resist wanting that for herself.
I am worried that your mere suggestions to her that she try to lost weight will hurt and anger her. She may subconsciously put more weight on if she gets resentful. I may be totally wrong here, it's just been my experience and I was constantly "encouraged" at a much younger age. One thing is obvious though, your love for your daughter comes through in your post. I think she's lucky to have a dad like you.
Best of luck with your continued success!