you're really lucky because nanaly is an archer with pirate range once AW'd, so she gets really long range with good aspd, and saint iris (also called b.iris or black iris due to her rarity) is basically a broken unit due to her skill that buffs def insanely.

as tenhou mentioned, her affection bonus is attack rigidity reduced, meaning she attacks faster. I think the rough idea is that there are 2 types of frames in this game relevant to a unit's attack/heal: idle frames (meaning the time in between each attack/heal), and attack animation frames. her affection bonus reduces one of the 2 frame counts (I don't remember which), and for future note, attack speed boosting abilities/skills pretty much all reduce one of the 2 frame counts, so the delay between each attack is shorter.

as for the AW path, it's something new in DMM called 2AW (2nd Awakening). b.iris is better off as oracle, because it gives her +10 range, which improves her broken skill (which increases def of units within her range) since that 10 range might well be the difference between reaching a unit or not in certain maps. still, this should be pretty far off for you and most likely you won't be able to afford it until 3 months+ of gameplay (likely more)