MrNorthSouth - First I hope your business trip is successful! It is great that you have taken the time to check in for your wife.
With Metformin, yes the side effects can be more dangerous to her liver. It is a blood test that they take. However, from experience here in the Caribbean - not all the blood tests listed on the form at my lab are performed. I think you should definitely look into if you have a lab that performs it. Here is a link about Metformin that goes through all ...
http://www.drugs.com/metformin.html
As far as numbers go, I try to focus on my health. I am an analyst by nature so I also tend to look at measurables. However, I have found several other ways that work. First, you could take a picture of her now. Twice a month or once a month, take another picture to compare. If you have her use the same outfit and stance each time it works best. You will be measuring the difference in how she looks. Second, does she have an old dress or outfit that is her favorite that she can no longer wear? She can measure her progress as if she can fit into it. I recently was able to wear a red dress that I wore 2x about 4-6 years ago. It felt GREAT!
(Personally, I have come to love getting on the scale and seeing what I weigh. So much so that a few months back, DH threatened to take it away because I was checking too often.)
Being stubborn and lacking self discipline can be hard in this endeavor. However, if she has positive support it will help her more. I know some women like to have their S/O or DH put up with the resistance and keep pushing through. The type perserveance is the factor that creates the most motivation. For example, if DH pushes at me too hard I just shut him out. When DH comes at me with a reason that seems like he truly listened to my feelings, I will jump right on it. (I can be a very stubborn person)
I wish you and your DW the best of luck!