Shadowheart's vanilla hair, in my opinion, is a good idea with a poor execution. I like the idea of Shadowheart having an alternative, unconventional hairstyle, but to me the way the front frames her face reminds me more of a helmet than realistic hair. While this could have been intentional (something something "Shadowheart aspires to be a True Warrior of Shar"), to me it just looks unnatural. It's so close to looking good, though, and I've seen many pieces of wonderful fan art that execute it so nicely, so I thought I'd try my hand at tweaking it to my liking.

Long-winded opening aside, what this mod actually does
- Adds more volume to her bangs
- Reshapes the fringes on the side of her face
- Resizes her circlet to fit her new bangs

This mod is not compatible with any mod that changes her first hairstyle, but should be compatible with any mod that changes her hair color (like Back to Black by Alkhan797), though I have not tested this.

UPDATE: I have added three new optional files, one with changes only made to the bangs shape which retains her curved side fringes, one with changes only made to the side-fringe shape which reatins her flat bangs, and one combining this mod's changes with LehLatte's Shadowheart de-creased hair. Only choose one option as they are not compatible with one another or the main file. They are installed in the same way as the main file (see below).

Installation: Extract the contents of the .zip folder into your Baldurs Gate 3\Data folder.
The file path should look something like [SteamLibrary Location]\steamapps\common\Baldurs Gate 3\Data.
Once extracted, the filepath should read [SteamLibrary
Location]\steamapps\common\Baldurs Gate
3\Data\Generated\Public\SharedDev\Assets\Characters\_Models\Humans\Resources" for the circlet and "...Humans\_Female\_Hair\Resources for the hair.

Uninstallation: Delete "HUM_F_NKD_Hair_Shadowheart_Evil_Circlet" from the "Humans\Resources" folder and "HAIR_HUM_F_Shadowheart_Spring" from the "_Hair/Resources" folder.

Note: The circlet is it's own mesh, which if used without the new hair mesh, will appear as if it's floating off of her forehead. Since this mod does not affect her second hairstyle, it is recommended to remove the circlet once she changes in Act 3. Optionally, you can also delete my version of the circlet and use the vanilla version by deleting the "HUM_F_NKD_Hair_Shadowheart_Evil_Circlet.GR2" from the "Humans\Resources" folder

Note 2: I currently have no plans on making a Selune/Act 3 version, but if you're interested in that you can use the aforementioned Back to Black Shadowheart
mod by Alkhan797 to do effectively the same thing by either using the "Starter Hair" or "Starter Hair Only" options from that mod :)

There are no known issues at this time, but please let me know if you run into any! I am particularly bad at spelling, so while I double checked I may have messed up the file path names, which would cause issues 😅 If it doesn't show up in your game please let me know!

Credits: Thanks to LehLatte for having open asset-use permissions on their de-creased mod

Mods shown in screenshots:
Basket Full of Equipment. SFW version
Noble Trickster's Garments
Companion And NPC Face Texture Tweaks
Asymmetrical Shadowheart Concept Outfit
Alternative Shadowheart Concept Tattoos
Makeup Remover
Shadowheart Alternate Hair (for brown color in last screenshot)