Welcome to saddoboxing John. Anyways I have a few ideas in regards to exercise and diet that may help pull your daughter out of that rut.

First just to get some things straight I need you to answer a couple questions. Does your daughter do any supplemental strength training such as weights? This not counting the typical boxing stint. This is just to rule out if your daughter is gaining more muscle which is preventing her from losing weight.

On another note I should say that a lot of people's bodies differ by their natural makeup, needs and reactions to certain diets and exercises. There's about 3 different categories of bodytypes that people fall into. Extomorphs which account for people that are have narrow shoulders, lean, and in general have a hard time building muscle. The second kind may be category that your daughter falls under. The second category is Mesomorphs, this body type is generally bigger, stronger, easier to gain muscle but on the flipside have difficulty losing weight/fat. I don't think that I'll have to go into the third category which differs from the two before mentioned.

Anyways some people's bodies have unique tendencies and needs that must be recognized for in order to know how to deal with them. A lot of the mesomorph sort of people in general have a body that hoards onto the fat produced by carbs. Reducing carbs can help as long as the body is getting enough. You experiment with reducing your daughter's daily amount in her diet, and record how her body reacts. You can not cut too much carbs from your diet because then your body would have to convert protein into energy and your body would also produce harmful toxins. A lot of people have done well to increase the amount of protein in their daily dietary intake. Protein takes more energy to burn, it's essential and there's an amount that your body needs. It'd be a good idea to find out how much protein that she needs.

Another thing that should be noted is eating balanced meals. If you eat too much carbs, or eat too much in general a few detrimental things will happen. For one you're causing a big insulin spike, which leads to more more carbs and fat to be stored as body fat. A big meal also sets you up for a big let down later when your blood sugar drops.

Even if she's working extra hard it still wouldn't be a good idea to to eat big meals. The effects are still the same, for example look at a lot of the guys in the NBA, they burn thousands of calories on the court, but the gorge themselves eating, this causes their bodies to hoard onto those extra carbs and fat.

Do you follow?

What would be then better is eating more smaller portioned meals throughout the day. Your body would get what it needs without putting it into storage. Getting enough protein in those meals are also necessary. This will also keep you from getting frequent cravings that is a result from lower blood sugar levels.

Some obvious things that should be taken to mind is gradually reducing the amount of calories during the day. This would mean eating smaller lean portions, and cutting out any junkfood for the most part. Don't be too strict with the diet, at least one or two days a week it is necessary to eat more carbs to maintain your leptin levels. Leptin is our body's antistarvation hormone that that sends signals to the body saying that we're getting enough to eat. A higher amount of carbs one day a week will maintain the leptin levels which will prevent your body from going into a fat hording survival mode. Some other obvious stuff is to stay away from junk food such as saturated fats, trans fats.

I hope this helps, next I'll go over some exercise ideas...