While the girl in the ad definitely looks to be of... questionable age, for an e-juice ad, I agree with what LMS62 said. She's an attractive girl, and looks like the over-eighteen-but-looks-15 classic "jailbait" (ew I hate that word) that so many advertising companies (and the Disney Channel) love so much. Good looking young women are used in advertising because they're an effective form of bait for both genders. To simplify it, they're aesthetically pleasing to pretty much everyone, so the ads they feature in lead to an increase in product sales and they and are hired for more advertising gigs and the cycle continues.
I also wouldn't say that the ad or a store being close to a school really counts as "marketing to children" either. There was a well-known brothel down the road from my school as I was growing up, but to my knowledge none of the preteen boys ever ventured in there. (They did knock on the door and run away giggling a lot, though.)
Obviously I find it concerning that kids with fresh babby virgin lungs are picking up vaping being they think it's "cool" and are uneducated about the various potential risks, and the sweet flavours of juice available increase the risk that kids will be attracted to it, but as far as I'm concerned as long as vendors continue to be reputable and refuse service to minors or any young person who can't produce acceptable identification, how and where they choose to advertise isn't an issue. Alcohol comes in sweet, sugary flavours too, but very few people villify it for "advertising to children" in the way people do with vaping.
EDIT:
So, ads for bras, make up and such are targeting males?
In a way, yeah. Men buy those things for their partners and (in the case of makeup) daughters and friends, afterall. Hell, many men wear makeup.
But also I'd like to point out that attractive, young women used in advertising shifts more products than adverts using unattractive women, regardless of which demographic the ad is aimed at. Even when you look at ads for plus-sized clothing or ads aimed at older women, the models chosen are
always attractive and have younger-looking features. It plays on the subconscious desire of many women to retain their youthful, pretty looks. There's a sort of "If you buy this product, you can look like this" element to it even though we all know consciously that a new mascara isn't gonna take ten years off you.