If she doesn’t mind boys (and a few girls) staring at her breasts, no problem. If she does, perhaps a bra would help.
As if boys (and some girls) wouldn’t stare if she was wearing a bra. Guys have a tendency to stare at boobs. Hers are pretty small, and maybe that cuts down on the staring, bra or no bra. As someone well endowed, I’ve always had guys stare. And of course, I was wearing a bra.
I've been on this earth for 50 years, and believe me, girls KNOW when they are attracting attention.
If they DIDN'T want it, they would wear more modest clothing.
I went to school in the late '70s, and EVERY one of my female classmates knew EXACTLY what they were doing.
Skin-tight Jordache jeans and form fitting shirts and tube tops.
(Which, by the way were banned in my school for that very reason, along with designer jeans that had zippers that went all the way to the waist.)
The exceptions to the rule were girls who had religious parents who made their daughters wear clothes that were non-revealing.