There's really attractive famous people who don't realize/appreciate how attractive they are, which leads to them making decisions that end up making themselves look worse. (Could name a few names here)
I'm obviously far from my 20s so I don't know for sure what sort of beauty standards are prevalent these days among people of Billie's age, but I could see someone who might not have thought of themselves as pretty doing things that could be sorta like boosting their self-esteem or whatever. Not to mention the whole "hey I have large breasts now" sort of change that no shortage of people, famous or obscure, had to experience in their teens.
If someone wants to try and take control in regards to being sexualized, is there really some big issue with that? Just because she didn't want strangers to sexualize her when she was a minor doesn't mean she's gonna wear a Niqab for the rest of her life. Billie probably could pull off the "Donna Reed as the old maid librarian in Pottersville" look from It's a Wonderful Life. But she's 22 now, so she'll do whatever.
Like most famous musicians, she'll be really famous for however long. I wonder if the industry will be more or less fickle with how things have changed with music distribution/production in this century.