It's important to choose your home wisely.

I have an account here on kbin.social, but I also wanted a dedicated lemmy account. I chose fmhy because it aligns with what I want: hearing every voice, for better or for worse. I considered beehaw due to their large gaming community, but I read about their philosophy and saw that they were trying to create more of a safe space for their users (suspicion recently confirmed). If someone wants a more positive experience without having to worry about trolling and harassment, beehaw would be the better choice. I am personally fine with treading through sludge to find hidden gems, so I made my own choice.

Bear in mind that defederation ~~isn't bidirectional. If beehaw decides to defederate fmhy, I don't care, I can still see gaming@beehaw and interact with users that live on instances still federated with my own. But the beehaw users are safe from from troll-friendly hosts, so everybody wins.~~ This isn't true, as pointed out by zinklog. It can still be worked around by having accounts in multiple places, but even with the eventual account migration feature, this makes it impossible for anyone to see everything in any one place. Maybe this can be fixed in the future, as the fediverse continues to develop?

To directly map it to the example of your friend, if she chose to live on an instance more like beehaw, she would still be able to interact with the federated community at large, but be better shielded. If someone tried to throw slurs at her from an instance with a lower standard, she wouldn't see it at all, and the person delivering the slurs likely wouldn't even realize it.