There are "sweet" sprays you can use on the tongue to get that effect, and they've been around considerably longer. I would imagine the same effect could be achieved, if that's what she is looking for it's possible the "craving" for sweets would be even more reduced, if squirted directly on the tongue.
I will say, I eat less sweets than I used to, but I also gained weight (on purpose, and I had to work on it though, although actually "understanding" what food tasted like was a big factor, that and the fact that it's really hard to eat when dealing with 18 months of pneumonia and on a rapid approach to COPD).
Nicotine is an appetite suppressant, too. If your daughter is vaping nicotine, that may be what is going on. In all honesty, I STARTED smoking in part because I was an avid biker and runner and I was spending the summer in England and had a bad hip from running and couldn't bring my bike. LOL, I FULLY intended (at 18) to Just Quit when I got home. It was the dumbest decision I ever made (and I've made PLENTY) and the one I most want to take back.
I don't usually suggest weight loss via vaping, and certainly not in your daughter's case. I had a monkey on my back for decades and it almost killed me.
I cannot in good conscience recommend vaping to a never vaper for WEIGHT loss. Vaping appears to be safer, but no longitudinal studies have been done.
Finally, and I don't mean to come across as rude, and I understand your concern for your daughter, but she is the one who needs to come on here and read and participate in this thread. Once I turned 18, I made my own decisions and my parents sometimes had trouble recognizing that. However, she is legal, of age, and I am hoping you will collect this information to provide too her, or encourage her to come here to discuss it. I kind of have a feeling she may vape anyway, but if you do have a motivator (a car! A membership to a great gym! Some other "something") I have found motivational behavioral interventions work best with kiddos. Mine has turned 21 TODAY.
I love him to death, he's made good and bad decisions, and I've offered advice (when requested) and that has usually been the best thing (for both of us). If she were underage, I might be singing a different tune, but frankly, she's not.
Best of luck, I really hope some of this thread is helpful.
Anna