Granted, the choice of wounding herself was rather extreme but it was the only way she could think of getting out of this situation.
Through her trials, she estimated that the ability of the beast was the same as her own blood. One that messed with the senses. Otherwise it wouldn't explain how the pebbles she threw never came back.
Since it was an ability that messed with the senses, she'll use the same strategy to defeat it.
Walking around the area where she's been imprisoned, she made sure to sprinkle a little of her blood in every corner, spacing them out evenly so the fumes could reach as far as possible.
The only issue with this strategy was how much blood she could afford to lose before she started to get dizzy and had to stop.
It was also a way for her to prepare for future battles. If she could mentally calculate how much blood she is allowed to lose, she could make plans around that value.
