my daughter is 210 pounds ???

Download an app called My Fitness Pal and log everything! It's SO easy to underestimate what you're actually eating. Id also recommend joining Slimming World (or weight watchers if she prefers), as the support you get from others can be so valuable.

Other things - drink lots of water, as lots of the time thirst can be mistaken for hunger. Try gentle walking for a total of 30 minutes of day - this can be split into 2 or three walks, and build up the intensity to a brisk pace as her fitness increases. It's always best to start more gradually and build up so that you don't set yourself up for failure. Good luck :-)