|Yes, 432 hit points.|
Before we go further, let's look at the different classes that make up her nature. Swashbuckler was a base class in 3.5 edition. It used light armor and finesse weapons. Both it and Duelist were heavily powered by Intelligence, dealing extra damage based on that when wielding finesse weapons. The Duelist class focused on having no armor but gaining bonus AC equal to the lower of their Duelist class level or Intelligence bonus. Neverwinter Nine focused on protecting allies and have a similar ability to a paladin's aura of courage as well as having some sneak attack damage and increased move speed. There was no actual magic in any of her classes.
Taken as a whole the most obvious is to make her a Rogue-Swashbuckler. However, it is also possible to do this character as a Monk-Kensai, focusing on the Duelist elements, or Fighter-Cavalier focusing on the training for protecting others. A Fighter-Banneret (Purple Dragon Knight) from the Sword Coast Adventurer's Guide also makes a good match. In fact, as Swashbuckler was primarily a warrior class, with a d10 hit die and fast BAB progression, the fighter might actually be a good fit and I think I will go with that.
For backstory, Meren was noted as a Veteran in the game I played, so I could go with soldier, but as you could tell if you watch the Let's Play I found it a bit unusual that she was marked as a veteran soldier of the war in which the game was telling me she was a baby in. That had to be one bad-ass baby. So I think I'll go with the Folk Hero origins the game harps on mostly from the original campaign.
As a further note, Meren had some serious skill in Tumble, Taunt, Bluff, and Persuasion, but not so much Intimidation. She also proved to be a good crafter of armor and weapons.
Tiefling 20th Level Banneret + Epic Boons
Saving Throw Proficiencies: Strength, Constitution
Tool Proficiencies: Armor-Smithing Tools, Weapon-smithing Tools, Thieves Tools
Acrobatics (Fighter) +12
Animal Handling (Folk Hero) +6
Deception (Skilled) +10
History (Skilled) +11
Insight (Fighter) +6
Persuasion (Banneret Expertise) +16
Survival (Folk Hero) +6
Epic Boons: Boon of Combat Prowess, Boon of Fortitude, Boon of Speed, Boon of Perfect Health, Boon of Immortality
Fighting Style: Two Weapon Style
Second Wind 1d10+20
Action Surge (2 Uses)
Indomitable (3 Uses)
Extra Attacks (3)
Silver Sword of Gith
Neverwinter Night Tunic (equivalent to Studded Leather Armor +2)
Most of her gear from level 15 (before she used the Neverwinter Tunic) is below.