She's cute, and she has a backstory full of Genshin Impact lore. But resources are finite in Genshin Impact, even more so if you are a free-to-play player. We'll help you decide if spending those valuable resources on Collei is worth it.
Should you level Collei in Genshin Impact?
From a gameplay perspective, we can't recommend Collei. Her multipliers and damage ceiling aren't very high, which shouldn't be all that surprising given that she's a four-star character that you can obtain for free. Instead, her kit seems to be designed to make her a off-field Dendro applier via her Elemental Burst, Trump Card Kitty.
The problem with this role for Collei is her Elemental Burst's field size and internal cooldowns. When she throws a kitten doll, leaving a Dendro field behind, the field isn't very large. The Dendro Traveler's Elemental Burst has a wider field, and can be made even wider by hitting it's center with a Hydro attack. The field from Collei's burst will apply Dendro on contact to an enemy, but then reapplies only three times over the course of a nine second burst. Such a lengthy internal cooldown makes this skill lackluster at best. By comparison, the Dendro Traveler reapplies Dendro to enemies in their Elemental Burst's field six times over 15 seconds.
If you love Collei's design or want to pair her with Amber in the overworld because they are best friends forever, go for it. There's always value in playing this game your own way simply because you love the characters. But since you can obtain the Dendro Traveler and all of their constellations for free via gameplay, we can't really recommend investing in Collei over them.
Want to learn more about the Dendro Traveler? Check out Best Dendro Traveler build in Genshin Impact – Weapons, Artifacts, & more! and Genshin Impact – All Dendro Traveler Skills, Talents, & Ascension Materials here at Pro Game Guides.