Boldir is a calm and collected individual, not prone to unexpected bursts of emotion. Upon meeting her, the player is instantly soothed by her presence as they feel no urge to prove themselves worthy of friendship. Boldir appears to be completely at ease with her place in the universe, for she doesn't seem to mind her worth (or lack of thereof) in regards to her existence. When she's on the brink of death in one of her bad endings, she isn't particularly upset with the notion of ceasing to live and breathe. 

She also appears to be incredibly well-read, given her ability to understand the details regarding destiny and causality. She casually debates the two concepts while on a stroll with the player, even though the player has some difficulty digesting the information she's dishing out. This might be due to her vagueness when conversing with the player, as she often asks rhetorical questions and gives thought-provoking statements. As it were, it can be deduced that she's well-versed in philosophy.

Boldir is noted to be a very cautious individual: after leading the player out of the cafe, she constantly checks her surroundings and takes numerous detours as though trying to shake off a stalker. This might be due to the fact that she knows too much information, culminating with an unknown troll trying to assassinate her in both routes. When trying to keep her aloft, the player notices that Boldir has four guns stashed away in her large coat, hinting that she's armed at all times to protect herself from dangerous situations. While her hat isn't given much attention in-game, her Troll Call bullet point reveals that the hat's interior is lined with foil to prevent any sort of celestial influence. Apart from that, Boldir is described to be rather muscular despite her short stature, and proves to be heavier than her appearance lets on.

I'd imagine her only speaking in whispers, as stated in the game.