Yep,
@Hammerblow pretty much nailed it (no pun intended). If your girlfriend has a PhD in biochemistry AND she's a world-class bodybuilder, then maybe it would be reasonable for her to contemplate it, but otherwise steer clear. I'm only being partly facetious here; DNP works through uncoupling oxidative phosphorylation, not through some neurotransmitter-mediated channel. In other words, it's a completely different creature from the familiar stimulants, and it's a total beast.
Main thing I'd add/modify in
@Hammerblow 's response is that perhaps your girlfriend should get her thyroid levels tested. (And maybe get a comprehensive metabolic panel while she's at it.)
Replying more directly to your question, ECA was pretty darn effective in SWIM's experience. Depending on your country, clenbuterol might also be an option, but even where it's available, weight-loss is an off-label use, I think.
Editorializing now, if your girlfriend is maintaining a clean diet and lifestyle, getting exercise, and has no underlying health problems, she probably doesn't need to worry about a little extra adipose tissue, unless a doctor has explicitly told her otherwise. If it's just a matter of aesthetics, I'm sure she's already beautiful just the way she is