"Hello. Thank you for applying to the company but we feel you aren't a good fit at this time. Thank you for your time and we wish you good luck"
or for general advice: "When applying to the company, please look professional at all times and be careful with your social media posts. We believe social media is an extension of our image as a company"
How hard is that? It accomplishes them not wanting that image without being a complete unprofessional idiot about it. Like, they have no room to shame her for unprofessional pictures when their own actions are just as much lol.