@JackieCat Awesome~!
I'll go ahead and list how each would likely play out, each have their sort of cool bits that could lead to other really cool bits. I don't really have a preference.
A friend could chaperone, keep her from getting into trouble and helping her grow and learn. Having someone who genuinely wishes her the best would be great in making sure she doesn't trust someone she shouldn't. That person would find that if they ever were in trouble, Rose wouldn't hesitate to help. This would probably be the most beneficial towards her aspirations, and keep her from deviating, from finding the world she wishes to help to be a hateful place.
A snake could play her like a fiddle, saying one thing but using her to their own ends. Having someone who acts like a friend, but truly only cares for themself, would play into just how trusting and naive she is. She would treat them like a friend out of ignorance, thinking they really were one, but when it becomes undeniable, her reaction would depend on the full story.
A monster, assuming in the literal sense, would really depend on what it is. Fighting monsters (in her mind) is all about keeping people safe from them. If there was another way besides killing or trapping them, she would very likely try that path. A friendly member of a species deemed a monster, if it showed that it was entirely benign, could have the same relationship as any other friendly person. A hostile monster, on the other hand, or one that doesn't clearly show it means no harm, Rose would attempt to fight.
But, if you mean a person whom is clearly shown to be evil and sadistic to others, Rose would certainly attempt to capture them somehow. Killing a person is unacceptable in her eyes as a means to defeat them. Her ability to do so would be directly relative to how they've shown to be evil. If they hurt someone right in front of her, she'll rally to their aid, and only be more determined in protecting someone innocent.
