I'm sorry. I just read your signature. At 14, she shouldn't be vaping anything, even unflavored juices.
No "vape shop" would sell to her without carding, so either she purchased the hardware online, where you click a button to say you are over 18, or someone purchased it for her, or someone got it for her.
Despite being an advocate of vaping nicotine or using snus, over smoking tobacco, we just don't know the effects of nicotine on the developing body and brain, and it is a psychoactive drug, though a mild one.
I know that when I came off of tobacco, my medications for bipolar, etc., had to be adjusted as one absorbs considerably less nicotine through vaping than one does via smoking.
The other concern over her using nicotine at her age, is that for some reason, teens are more likely to quickly become addicted to all substances than adults whose frontal lobes are done maturing.
Not only that, those who have become addicted in their teens have a harder time getting off of those substances than those who became addicted in their mid-twenties or later.
The "holding it for a friend" is classic teen addict/druggie BS.
Nicotine does interact with ADHD medications though off the top of my head, I can't remember how exactly.
If you want more info on vaping as regards vaping for nicotine or flavor usage, hardware, liquids, etc, feel free to PM me. I'll be happy to either answer your questions to the best of my ability or find answers for you.