Start off slow. By slow I mean walking. Do alot of walking. I started off walking a few miles and had gotten up to walking 13 miles before I started throwing some running in. You want to try to stay as low impact as possible untill your able to get some weight off.
Choose your protein carefully. I would say that with women choose a soy protein over a whey protein. It tends to produce umm breasts (men avoid). I personally stick with Isopure due to it having 0 Carbs and others that say low carb can have alot of hidden sugars.
Start taking liquid Amino acids. This is a good source of protein and will help keep unwanted loose skin off. (you're both young and this should help with the elesticity of the skin, keeping you from having unwanted scars from surgery).
Lastly get lots of protein in your diet. This will help with skin, hair, body, muscle etc... When you hear the doctors say get plenty of protein take it as gospel not just b/s. Whats the since in looseing a 100 lbs but going bald and having a bunch of loose skin? Do it right and don't exchange one problem for another.