5'7" and 127, unless she has a teeny tiny frame, is quite thin already. If she wants that ripped look, that means getting her bodyfat down and that's all about being scrupulous about your diet. For a woman to sport abs you're talking about being in the vicinity of 14% to 18% BF, that's requires discipline. You have to make sacrifices, no cookies, no sweets, etc., etc., etc.
Depending on where she is physically, what she wants to look like, she probably either needs to focus on gaining some muscle while gaining minimal fat (or staying at about the same current weight) or get her diet really nailed down. She's already thin, a diet supplement may just potentially have her starving herself (while not feeling hungry) which won't do a thing to enable her to build any muscle and she might end up tearing down her existing muscle and she'll be stuck with a slower metabolism in the end.
I mean, does she want a certain look, or is she more concerned about the numbers on a scale? If she wants to look a certain way she needs to toss the scale out and focus on achieving the look.