Jingliu, ice destruction, afflicted by mara
She can actually work well with Blade as her team hp drain will give Blade more charge stacks. It is actually scary how well she and Blade can work together.
Of course she benefits from healers such as Luocha. Jingliu arguably needs a healer more than Blade as Blade can at least self-heal.
Bronya, Tingyun, the usual suspects are good for her. She benefits from dmg bonus buffs.
In her special moon state, she is SP neutral. But she will need to gain syzygy stacks to enter that state.
In her moon state (Spectral Transmigration), she gets a bunch of crit rate. Also her skill gets enhanced to blasts and will consume hp from all members of the team to buff her atk.
Her E1 and E6 give her a bunch of crit value. Her E4 allows her to buff her atk even more. So Jingliu is a character that can get high atk and high crit. So in this sense she is sort of like Itto.
The only thing she wants more of is damage bonus. Her E2 gives her E 80% dmg bonus after using Q.
The goal is to stay in her enhanced state for as long as possible. This will usually involve using her Q during her moon state to gain stacks and prolong the state. In her enhanced state, using her buffed skill will consume 1 stack. When she reaches 0 stacks her enhanced state ends.
Outside this buffed state, her E gives her 1 syzygy stack. Her Q also gives 1 stack. When she has 2 syzygy stacks she enters the enhanced state.
Her technique can freeze enemies and give her 1 stack when entering battle.
Before E6 she can get a max of 3 stacks. Her E6 increases the cap to 4 stacks and gives her 1 extra stack when she enters the enhanced moon state.
Because she gets so much crit rate in her enhanced state, one can usually go for a crit dmg headpiece. 4p Longevous Disciple is good, giving 12% hp and 16% cr. So just from this relic set and the 50% cr buff, Jingliu can reach 66% cr. She can then just full-on invest into crit dmg.
While Yanqing's Q gives 60% cr, it requires energy and lasts 1 turn. By comparison, Jingliu can activate the 50% cr buff via skill, and it can last several turns.
Her hp drain will drain allies even if they are shielded (for example by Gepard or Trailblazer).
Some mara enemies (shape shifter) and Sam can also drain their hp.
The way she laughs is kind of crazy.
In Genshin, Jingliu is a cryo sword user. Using E gives 1 syzygy stack. Using Q gives 1 stack. Think of stacks like Alhaitham's mirrors. When she has at least 1 stack, she gains cryo infusion on sword. Each stack lasts say 4s (like Alhaitham's mirror). So if she has 2 stacks, her cryo infusion lasts 8s.
When she has 2 stacks, she enters a buffed state. She will gain 50% crit rate and greatly increased aoe on her NA/CA, and she will drain the team hp to buff her atk. Moreover, using her CA during this enhanced state will drain the team hp (or one can put a Xiao effect where the team hp drains once per .5s during her buffed state). This buffed state will end when she has 0 stacks. Stacks can be refreshed or gained via E and Q.
If one wants to make this more like Alhaitham, the more stacks she has, the more scaling her NA/CA do (or the more dmg bonus it gets). Also, using a CA can give a stack (and say this effect can occur once every 12s, like Alhaitham's passive).
Just want to emphasize that 50% crit rate at C0 and without artifacts is kind of nuts. As of 4.1, there is probably no Genshin character that can get that much crit value in their base kit without artifacts or constellations. For example, Scaramouche can buff crit rate by 20% when absorbing cryo.