Lastri has terrible stats: Str 8, Dex 19, Con 12, Int 13, Wis 10, Cha 11 at level 4, implying pointbuy 24. A decent initial selection of feats (Luck of Heroes, Dodge) fails to make her useful. There are much better cohort options in the campaign.
As of patch 1.22, Lastri's stats are greatly improved: Str 10, Dex 19, Con 14, Int 14, wis 10, Chr 12 at level 6, implying pointbuy 32. Also, Lastri loses Luck of Heroes (which she would get automatically at Swashbuckler level 11), and gains Weapon Focus: Rapier; a bad feat for her because a rapier does not benefit from Weapon Finesse in the hands of a small-sized character.
Although listed as true neutral, she starts pretty far from the center of that alignment, having only 36 points on the chaotic-lawful axis. This is unusual for an NPC.