I have turned against the BOS siding with the railroad and manipulating the institution. However, after the attack from the BOS on the railroad, I got a mission to get a Vertibird from the police station. No problem killing BOS bastards, but Haylen is there as well so I wonder is there a way to spare her life?

As a lovely Institute director, I'm happy to report if you do intend to visit the police station, much murder and carnage will happen. To haylen as well.

On a serious note, take some powerarmour, be ready to blow everyone up, but you can try to avoid murdering her, just be ready to heal yourself and the likes.

I play as a "one shot sniper" so I don't use the power armor. I could avoid killing her but she keeps on shooting at me and we can't have that, can we?

Murdering everyone, and sparing her is a worse fate lmao.

The Brotherhood are a tightly knit bunch, killing all but one, is basically like what was done to you at Vault 111.

But, I suppose if you want to play something more wicked...