She could've just bite her tongue and its also quicker.
biting your tongue is an extremely slow death and isn't portrayed well in manhwas. Even if you bite strongly enough to sever an artery, youd die in fifteen to thirty excruciating minutes, where you'd be choking and just having a horrible time. Jumping from the carriage whilst another one was incoming is better since the chances of her dying on impact were high. But yk if the impact didnt kill, then she can resolve to biting her tongue.
I feel like we are looking at this from 2 extremely different perspectives maybe you just have more will power than me because I do not think I could do something as painful as biting my own tongue off... however jumping out of a moving carriage, well that doesn't hurt until impact is made. Idk to me the idea of biting off my own tongue is just impossible, but like jumping from a moving car to me seems less painful, at least until impact.
This is the misunderstanding i like