Number has Rein beat physically, so if it comes down to melee, Rein stands no chance. If we go by marksmanship, Number is likely a better gunner, but Rein a better sniper. Number can further increase his power via his ability, which would overkill Rein in melee. Rein has faster reactions with her Sigil which would allow her to dodge any bullets he would shoot, but not necesserily his CQC as she still has to concentrate and she can't fight.
It's often stated in the manga Rein avoids combat as much as possible, and generally resolves to running away with most encounters, refering to herself as a "master of retreat". When that option isn't available, she uses every piece of information at her disposal, analyzes and examines her surroundings, tools and knowledge, calcs probabilities, and then acts accordingly to have her survive by the end, either though psychometry, hiding, planting traps, baiting, or whatever else. If Rein witnesses Number's ability and manages to escape, she will deduce his strengths, weaknesses and limitations, as she has been doing in the series for a while with anyone she meets or even just heard of.
I honestly don't know how Number's talk-no-jutsu would affect Rein. She already doesn't seek conflict to begin with and always prioritizes survival over victory, so Number talking her out of fighting would just push her further into her retreating tactic, psychometry-ing her way out of the situation.
I assume Number will want to get to Rein asap, while Rein will want to avoid Number as much as possible, turning into a cat-and-mouse situation.
