I don't actually think this ad is offensive. The reason, is because when I was a teenager, I knew hordes of girls for whom this kind of ad is basically a mirror of their life.
"OMG BOYS AND MAKEUP AND EWW NERDS ARE GROSS AND LET'S GO SHOPPING TOGETHER!"
That line isn't just a stereotype. Come on, you've all seen this phase. It's that age around 13-14, where girls are seeing their hormones fly and most of them clump off into cliques that are centered around one-upping each other and trying to get dates to the school dance. The few outliers bury themselves in books and decide not to care, and ending up as the plain-looking folk who don't join the main social crowd. The entire society polarizes until about age 20, the socialites and the nerds drawing a line down the center of the metaphorical treehouse and keeping to either side out of mutual distaste.
As such, what this ad is trying to appeal to is teenage girls who aren't already nerdy and into science. Those who are already there, don't need to be marketed to. The girls who haven't bought into the American teenage girl fantasy, don't need or want this ad. This is for the girls who think that nerds are not sexy, that liking science means you have to give up cosmetics and caring about your appearance past "wearing clothing," that you can't be fashion-conscious and work in a lab, that "beauty" and "intellectual work" have to be mutually exclusive. Even if this opinion fades in adulthood, because college is right at the tail end of the phase, you have to appeal to them before the stereotype wanes away into more complex opinions. This whole conflict is as much nerd-dom's fault as the socialite crew's fault. "People who like makeup and dresses are shallow" is just as bad as "people who like science are ugly and weird." There are too many studies showing that women start hiding their intelligence around teenage-hood, because they don't want to sacrifice their social lives and non-nerdy interests for learning.
Is it really flagrant and garishly done? Absolutely. Is it sexist? No. Because the people who this ad would appeal to, absolutely exist, and in large quantities.
I'm honestly glad someone is trying this.