The who the heck was that?
Edit->Its believable not to have trauma, if she only remembered dying 5-20 times then I can see it.
But after dying 100+ times I doubt you would fall into despair, once the wave of realization hit you not care as much because you should have gotten use to it.
Knowing the pain in one life increases your tolerance in another.
I imagine Subaru would not even scream after 100 death, 25+ gave him a high pain tolerance.
So using Subaru as a reference, the pain and death toll is too high for her to care.
(Maybe Subaru is not the best example, but I am just using him to say if you experience something bad continuously, you deal with it better.
I doubt this girl is 100 percent sane... same thing for the blonde heroine.