Sorry, I didn't notice this earlier.
At 150 lbs, her maintainance calories are around 2100 kcals.
She is probably eating below her basal metabolic rate, which will slow down the metabolism.
There is no way she is going to build any muscle on those calories.
You can also get fat on a calorie deficit, our bodies protect us from starvation.
The way they protect us is to hold onto the fat and burn lean tissue, especially when you don't have a lot of extra fat, and at her height and weight, I don't think she could have a lot of extra chub on her.
I would also recommend she experiments with her diet and see if eating carbs also helps with her goals.
I weigh 140 lb and my competition diet is 1800 kcals, and I am stripping fat and still maintaining muscle, naturally. My diet is high protein, high carbs, low fat.
I would recommend that she starts to track her calories and start to bring them up to around 1700/day if she really is eating that little.
In all honesty, I wouldn't advise any fat burners, I think that the issue for her if she wants to lose fat is to work on her diet, do some more weights.
Tom Venuto's e-book, Burn the Fat (with cardio and training) Feed the Muscle (you have to eat to have a great physique) is named that for a reason.
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