Lysithea and OG Azura are almost identical in terms of physical bulk.
Azura: 36 HP and 21 def (31 atk and 28 res)
Lysithea: 37 HP and 21 def (41 atk)
To one-shot Lysithea, a blue unit without TA needs 49 atk, and with a 14mt weapon, Azura gets 45 (47 if the weapon is atk refined or if she gets a prf). Resplendent (or +atk) would give you enough atk to reach 49 and one shot her.
But if Lys initiate combat, she will have 73 atk (58 against a blue unit), and will inflict -3 res from lull, and -30% res from moonbow. A regular Azura needs 36 res to survive that. Now, if she is the same Azura as above (ie, resplendent and atk refine weapon), she gets +2 res and +7 hp, being at 43 hp and 30 res, now in this case, Azura needs only 26 res to survive, which she does have.
This is all considering neutral IVs and no buffs though
edit: Also, this is considering a distant counter Azura technically, since she will be doubled by Lysithea, she needs to kill her before the followup to survive