Rina's Quirk is called 'Sharpshooter lens' and will be a regular '3 tomoe Sharingan' that mutated by merging with a copy of Mei Hatsume's quirk 'Zoom' (the golden iris with a crosshair on it that allows the user to see up to 5 km away, basically a knockoff Byakugan), the appearance will be the same as Mei's eyes whilst not being used; whilst active will gain 3 black tomoes.
The passive ability of her quirk whilst not activated is being extremely accurate in shooting or throwing any items or weapons, this will happen instinctively and can be called an innate talent.
The active ability of her quirk would be to see up to 5km away and to summon a single truth-seeking orb which she would usually manifest as a pistol or throwing knife/dagger (both may increase with training). Much like a Sharingan, she will have an eidetic memory and will have her perception of time slowed along with gaining inhuman accuracy and reflexes far surpassing her passive state.
She will have some basic training in Thai boxing and grappling for close range (since I have some experience in those I can actually write about them without sounding like an idiot). She will have extensive training in using throwing weapons such as balls (regular truth-seeking orb and for sports such as tennis), knives, darts and maybe shuriken and kunai.
She will also have a very high skill in marksmanship allowing her to use most guns to hit targets at any range she can see with nearly 100% accuracy so that she can neutralize villains with non-lethal means or lethal if the situation requires it (the pro hero snipe uses a gun to literally shoot out peoples joints so they can't move, he did that in the USJ attack).
I am planning on having her fighting style mainly focused around marksmanship but I may incorporate using the truth-seeking orb to make an armour similar to Kirishima's 'harden' quirk to fight unarmed, or to make a bo staff as Momo Yaoyorozu uses.