ABSOLUTELY NOT! Don't even get me started on that horrible storyline...

100% Yes

Your first instinct while worried about dying should really not be kissing your kind of ex who is currently dating your best friend. How exactly are you supposed to come back from that?

Well, I do ship Leyton and adore Brooke. I can put myself in Brooke's shoes on this one. Peyton has done noting wrong in my opinion the second time. She kissed Lucas, the boy she loved because she thought she was gonna die. And then she confessed about her feelings towards him instead of hiding to Brooke. Still, I get how Brooke felt. She was scared the whole BLP thing would happen again and she felt threathen. I'm pretty sure I would have reacted the same way.

I'm just going to quote Rachel Gatina.

Okay, let me get this straight. You don’t have feelings for Lucas anymore, Peyton does yet she’s willing to hide those feelings if you ask her to, sounds like a pretty great friend to me.

By default if you're about to die, or at least bleeding to death, I think you get a free kissing pass.

Agree with Ade. And not because Brooke is my favorite because I do ship Leyton and I do believe she actually over reacted over Alex and Julian in s7. But in that situation any actual person with feelings would react that way.
Oh and btw, if the exact opposite thing had happened the LPers would totally understand Peyton reacting that way. But not Brooke, no, she's a drama queen whore.