As well as a bit more of an insight to what the siblings were like back then, because looking at this:

“Some resisted” 

“Others called it fate, when the aliens opened fire on us”

Arcee is clearly not just speaking broadly with those lines.

No. Very specific memories in mind with those.

Because it looks like Arcee didn’t want to take part in all of the slaughter and tried to defect, to run away.

But bro steps in and talks - surprisingly gently for him -  Arcee into coming back.

That first line is what Arcee did and that second one is something that was said by Galvatron in the ensuing twin conversation.

I wonder how the rest of the conversation went, that day.