Kresh is space fugu in leaf form. Why does any sane person want to partake in that willingly?
Partly it's to thumb our noses conceptually at all the pureblooded Civire and Deteis who've sneered at us over the years (real or, in Aria's case, mostly imagined) (she did get sneered at; she just doesn't remember it. Also, in reality, it was mostly pureblooded Achura).
Partly it's to join those self-same Civire and Deteis in the experience of sipping potential death from a cup. A certain amount of cultural self-respect is tied up in the act, as being able to face kresh is something only "real Caldari" can do.
Also, Aria's faced a couple incidents of immediate, personal danger in her kinda-sorta couple months of life, and (while she wasn't especially called to) didn't act especially effectively. In one case, she more or less locked up; in the other, rescue arrived before she could do anything / be required to do anything more daring than radioing for help.
The latter situation had her trying to figure out how to use an Amarrian sidearm while Blood Raiders cut through the door onto the war barge bridge she was on. She wasn't sure at the time whether the gun was going to be for them or for herself. The experience traumatized her enough that she essentially holed up in the SFRIM living quarters for a couple weeks after. She's still having nightmares.
A nasty little voice in her head has started calling her a coward, which erodes her confidence. It's not going to shut up until she faces death without cringing at least once, and kresh is far and away the least hazardous of her options.