Anyway, my own thoughts in no particularly organized order.
Women (and men as well while we're at it) should feel free to wear whatever they like, and should feel free to post pictures of themselves wearing whatever they like. There's nothing wrong with looking good, nothing wrong with taking pride in it, and nothing wrong with sharing pictures of things you take pride in.
The primary reason Dunne is able to make so much money from endorsements is because so many men like looking at her, and the primary reason men like looking at her is because they find her sexy. There is nothing wrong or shameful about Dunne taking advantage of that; I'm just stating the reality of the situation.
We live in a society where people need money to survive. And if you look good enough that you can make money just from looking good, then I see nothing wrong with doing so. Looking good -- and even flaunting one's good looks -- is not in any way an invitation or justification for harassment.
Livvy Dunne deserves respect as an athlete and as a person, completely independent of how she looks or how she makes an income.
Now all of that is a discussion of how things should work for adults in an ideal world. And there are two significant complications to the situation: first, that we don't live in an ideal world, and second, kids are likely to try to emulate Dunne.
In the real world, women who do this sort of thing tend to get subject to harassment (I mean, even more than most women). They shouldn't get harassed, and it shouldn't be their responsibility to try to avoid harassment, but the reality is that it does happen.
Combine this with the fact that a lot of young girls likely see how successful Dunne has been, and may try to emulate her by posting similar sorts of pictures on social media, which potentially puts them at risk of harassment or worse.
I'm not sure how these complications should be addressed. Livvy Dunne is not responsible for the behavior of her followers; that includes both the men who harass her and the young girls who may try to emulate her. It would be great if men were more responsible in their behavior toward women, and it would be great if parents were better able to monitor their kids' behavior on the internet. But standing around saying "wouldn't it be great if" fixes nothing and protects nobody.
I'm not sure what should be done to protect Dunne or her younger fans, and I'm not sure who should be the ones to do it.