First of all, at 5'8", 210lbs your girl simply does NOT need to be using clen right now.
Before you can lose fat to get in shape, you need to get in shape to lose fat. That sounds contradictory, but it isn't really when you think about it.
Rather than starting up something harsh like clen, she needs to spent at least 6-8 weeks dropping weight and losing fat on her own. This isn't a knock against her. But if she starts clen now, she is eventually going to plateau with the results in a month or so. And then what? Use more? Don't.
Instead, drop what weight she can now on her own naturally with training and diet adjustments, then when those efforts slow a bit in the future, you incorporate regular fat burners and ECA to kick it up a notch and then later when the effects from those slow you can resort to clen to kick it back up again. But using clen right off the bat with her stats is only a recipe for long term frustration and failure. Yo-Yoing WILL occur.
Next with liquid clen, it is really really hard to get an accurate dose each time. when trying to capture an exact amount of mcg's in a liquid solution per dose, there is no way to ensure accuracy.
Instead go with tablet form.
Better yet, instead of clen, go with Albuteral. That is just like clen in terms of results but without the nasty side effects that clen brings like headaches, the jitters, constant nose sniffling (for me) and the flushed/hot head feeling.
Unlike some people who compete and use things to simply look good on one day at a time (contest day), I would wager that your girlfriend is obviously looking for something else that will last for the long term in her body transformation. Which is why you should go a LOT slower in weight loss and toning than some people do in 12-18 weeks when ripping up for a show. If you rush your body into a state of change very fast, it is going to be a constant struggle (read : frustration and being miserable) to try to hold it there. It is like a rubber band, you stretch it fast and it snaps back to it's original shape. But if you stretch it slow and steady, a little at a time you can end up with it more flexible in the long term. Same thing with your body. You take it a step at a time. You set goals. You reach Goal #1 and you stay there for a little while, so your body can adjust itself to it's new condition and begin to accept that state as it's new "normal state". Then you use that state as the launching pad afterwards to reach Goal #2. Stay at that phase until your body accepts that current condition as it's "normal state". Then you shoot for Goal #3. If you have a relapse, or can't continue on for a while (injury or family matters, etc..) then your body will revert back to where it was at Goal #2 since it considers that "normal" now. It is like setting little checkpoints for yourself.
This probably isn't what you wanted to hear and it might sound negative and pessimistic, but trust me in the long term scheme, this is where the best/most benefits lies.