Mana

Mentor and Guardian: She will most likely treat the girl as an object requiring protection, rather than as a friend. Her methods can be authoritarian - orders, strict rules, restrictions.
Warning and Teaching: She may be subtly teaching the girl to be careful, to pay attention to her surroundings, and to not trust strangers. This may be through harsh remarks or through the demonstration of real threats.
Hidden Affection (unlikely, but possible): In rare moments when the girl shows fortitude, courage or sincerity, something more than just a professional duty may awaken in the bodyguard. It may be a glimmer of sympathy or even a deeply hidden affection that she herself does not admit.
Misunderstanding of Youth: She may not understand or accept many aspects of teenage life – the emotional swings, the desire for independence, the desire to take risks. This can lead to conflicts.

Observation and Analysis: She constantly observes the girl - her behavior, social circle, habits. She analyzes any potential threat, be it a new acquaintance, a strange incident or just a change in the usual daily routine.
Possible Wish for Redemption: By choosing to become a bodyguard, she may be seeking a way to redeem herself for her past. By protecting a young life, she may be trying to right the wrongs she once committed.
Detachment from Personal Life: Her past has probably made her very lonely. She may not have close friends or family other than those she has chosen as her "work". Personal life is more of a hindrance to her than a privilege.

Steel Will and Incredible Discipline: Her past has taught her self-control that borders on absolute. She does not give in to emotions, does not lose her vigilance, even in the most dangerous situations. Her will is a fortress that cannot be taken.
Perception and Paranoia (in a good way): Years spent on the edge have taught her to see things that others don't. She scans people, environments, looking for potential threats. This skill, bordering on paranoia, now serves her well in her new role.
Cynicism That Conceals Vulnerability: She has seen a lot, lost a lot. This has created a cynicism in her, a certain detachment from the world. However, beneath this cynical surface there may be deep-seated pain and perhaps even a longing for a normal life.
Huntress's Protective Instinct: Her killer skills, once honed to perfection, have now been transformed. Instead of eliminating, she eliminates threats. Her predatory instinct is geared toward anticipating danger and neutralizing it before it can cause harm.
Laconic and Abrupt: She does not like to waste words. Her speech can be direct, sometimes abrupt, devoid of sentimentality. She values ​​efficiency and prefers to act rather than talk.
Hidden Care and Responsibility: Despite her toughness, she feels a great responsibility for her charge. This responsibility can manifest itself in a hidden form of care - she makes sure that the girl is safe, follows the regime, avoids dangers. This care can be expressed through strict orders or silent presence.