Jean is an Anemo sword type user that is a mix of both offense and support. The thing that makes her special is that she has a 50% chance to heal all your party members when she uses normal attacks, and it has no cooldown, and the heal scales off of her attack stat. This means that you can build her high attack DPS style and her heal will also end up getting stronger. Since she's an Anemo type, this will also help with elemental chaining since swirl will essentially work with most of the other elements by expanding them. Her elemental burst is also a 4 in one ability. It has burst heal and damage on initial cast, plus HP regen and Anemo damage for a few seconds within the field. The main downside is that Jean can end up pushing enemies away from the circle when she uses it.
Even though Jean works best as a support, she can also be built to fit the role of a DPS quite well. There are 2 ways to build a DPS Jean: Physical DPS, or Anemo damage style. The physical DPS version is more consistent, and the better option if you have no other viable damage dealer. Her normals and charge attack can reach high numbers, and she's fairly easy to play. The ideal target for artifact sets are 2 piece Gladiators Finale with 2 piece Bloodstained Chivalry, using phys dmg bonus on the cup, and crit rate/dmg on the crown.
For Anemo damage version, go with either 4 piece Viridescent Venerer, or just 2 piece Viridescent with 2 piece Gladiators Finale. With this build, her normal attack will be noticeably lower, but an increase in her skill and burst damage, so you'll want to use it more often. This version is also a pretty good sub DPS if you already have a main DPS. Simply switch to Jean when her skill is up for a quick blast that deals good damage. Be sure to use Anemo damage% on the cup piece as well.
If you only bring Jean on the team for the heal/burst, simply focus on either 4 piece Maiden Beloved, or 4 piece Viridescent Venerer for an added benefit of reducing enemy's resistance. Her heal scales off of her attack stat, but if you only focus on her supporting ability, then you won't really need to level up the artifacts to max level. If you want it to deal good damage to help with the team, then full Noblesse Oblige, or 2 piece Noblesse with Viridescent is the way to go. Ultimately, it really depends on your playstyle and what you want Jean to be able to do.
The best support weapon to give to her is the Sacrificial Sword. It's an amazing weapon that can let you do 2 elemental skill in a row. It's especially useful on Jean because she can blast enemies into the air to deal fall damage, which scales off of their HP. A high level enemy can take about 20,000 damage if you blast them into the air. Being able to do it twice will essentially be free 40,000 damage even if you don't build her for a damage dealer.
She can work in any team if you are using her as a support, but there are still really good pairs that you can do. Jean and Venti is a strong pair because it's double Anemo. Not only does this give an elemental resonance passive, energy generated will benefit them both, and they work well together in general. Using Venti's burst, enemies in the area will get sucked up and drop down close to each other after it ends. Simply use Jean and hold her elemental skill to blow them all up into the air for fall damage, and generate some energy. If you use sacrifical sword, you might be able to do it again for a lot of extra damage. Other than venti, there's also Beidou, Chongyun, Xingqiu, and/or Bennett as really good general options as well.
"Focusing the might of the formless wind around her blade, Jean releases a miniature storm, launching enemies in the direction she aims at, dealing massive Anemo DMG.
Hold At the cost of continued Stamina consumption, Jean can command the whirlwind to pull surrounding enemies towards her front. Direction can be adjusted. Character is immobile during skill duration."
"Calling upon the wind's protection, Jean creates a swirling Dandelion Field, launching surrounding enemies and causing Anemo DMG. At the same time, she instantly regenerates a large amount of HP for nearby allied units and all party members. HP restored scale off Jean's ATK.
Continuously regenerates HP for one ally and imbues them with the Anemo attribute.
Deals Anemo DMG to enemies entering or exiting the field."
Hits by Normal Attacks have a 50% chance to regenerate HP equal to 15% of Jean's ATK for all party members.
Let the Wind Lead
Using Dandelion Breeze will regenerate 20% of its Energy.
When a Perfect Cooking is achieved on a dish with restorative effects, there is a 12% chance to obtain double the product.