In my opinion it's too early to judge her loyalty (only 3 chapters have passed). In the future we will have plenty of opportunities to test her loyalty and see how faithful she is to our protagonist and whether you can really trust her with your back. "Adventurous" - I'm not sure what you mean by that. I noticed that she likes to get involved in other people's business, so maybe that's what you mean? "Gorgeous" - yeah, like most of the LI's in Ocean's games, thanks to him for that. "Gamer Girl" - you're a gamer, so having her share your hobby gives you satisfaction, it's understandable. What do you think about the disparity in their sex drive or her violent tendencies?
For me, the trait of loyalty has two sides. The first is fidelity in relationships: she does not cheat or do anything with other without the permission of the MC. Ocean seemed to reassure us of this, or at least repeated several times, that NTR is completely avoidable, even if it's turned on. You will have to constantly neglect Miru and encourage her to the idea of an open relationship so that she will start doing NTR things.
Another part of her loyalty is that she takes the MC's side in his business and watches his back. Until recent she does just that, she helps MC reunite with his family, smooth things out in relationships with "old friends", and generally helps him with everything. We'll see what happens next.
Adventurous - I mean she's creative and likes to experiment sexually, like sudden public sex in the gym shower. MC won't get bored with her.
Disparity in their sex drive? C'mon, this isn't Nika, and the game isn't SG, this is Willie "The Snake" Zane. He will boink all the female population of the Wollust if he has to. He's just playing hard to get and teasing her, but the limpy wormy is definitely not his case.
Violent tendencies? I'm not sure if I follow. Do you mean she punches him from time to time or plays an evil demon? This is part of their foreplay, I guess. She's just pretending to be an angry dominant girlfriend. And given her height and build compared to him, it looks simply comical.
If she really wanted to hurt this meatbag she would have to hit him in the nuts, neck, eyes or jaw, something like that. Otherwise she will just simply bounce off him like a ping-pong ball.
But yeah, she keeps an eye on him and lets him know when he's being a complete asshole. And I am absolutely sure that she is doing this with his full unspoken consent and he is glad that he has someone next to him who can tame his temper. A guy who just left the most important people in his life and never looked back will not put up with the rudeness of a girlfriend, even one as cute as Miru, unless he himself wants it and does not consider it rude or violent.