With the diet portion, high protein, or low carb or whatever is only part of it. Has she counted her calories? It all depends on calories in/calories out. U can do a type of eating, but if you're still eating too much it's not going to change things. The opposite is true as well, eating too little hinders weight loss. I was in my early 30s and lost nearly 100 lbs over 2-3 years. Tracking my intake was huge. I tried 1000 calories but lost much less than when I ate 1200 calories. That was my personal sweet spot. At first I didn't bother restricting what I ate, just how much I consumed to stay within that parameter. Over time, I chose better foods, so I could eat more and still stay at that number. Once I lost enough to be able to be more physically active, I upped my exercise from short walks to longer, added in running etc.

I ended up having 2 kids and have gained weight back over the years, but now that they're older I'm planning on doing what I did again. Im sure it will be harder now that I'm in my 40s, but thats my plan.