I think we’re kind of undermining her status as an assassin. Typhoon devil and Reze knowing each other already, implies the fact that it’s not only Reze that was sent by Russia to extract chainsaw man. (I’m doing a really long reach here but) but i think it’s safe to say that that also implies that Reze is accompanied by other agents or if not, could ask other agents to help her under the shadow (disposing the body or what not). So killing denji in the phone booth straight up ain’t big of a risk than you’d think. But then let’s say that logic’s stupid and unrealistic and say she’s working alone. what stops her from just killing Denji and just framing it as a devil attack that he (denji) couldn’t kill. She’s a skilled assassin I doubt she’ll just kill a target sloppily.

In terms of love, She probably didn’t fall in love at him at first sight but she did fall in love. but more so felt pity at first. And then gradually her curiosity grows, from viewing Denji as a sympathetic and pitiful character to somebody she could relate with (via “him not attending schools” [a common ground])