There has been a slew of Genshin Impact leaks featuring Yelan's kit as of late. Sadly, none of those leaks feature any gameplay or other concrete evidence. All that's known about her at present is that she's a 5-star Hydro Bow user and that she has a model (at least based on current Genshin Impact leaks).
Note: Travelers shouldn't believe that every Genshin Impact leak is legitimate. Leaks aren't automatically legitimate just because they come from NGA. More often than not, there are many fake leaks.
Information from those leaks is shared here for the sake of aggregating various news sources. Whether the reader wishes to believe it or not is up to them.
The first unverified leak to cover comes from NGA, with a better translation coming from u/lemonmoon23:
If it's true, then that means Yelan is yet another sub-DPS option. The HP% of her kit might not necessarily mean that she has to build HP, with the example being Xingqiu's healing also scaling off of HP. However, no specific numbers are given here.
The first part of this other Reddit post addresses Yelan's kit. If it's true, then it means that she would be terrific for Vaporize teams. It also states that her Main DPS potential isn't as good as her support potential.
Like with the previous leak, there is no specific mention of how her kit is supposed to work. There aren't any numbers or expectations that one should have of her, except that Yelan will be useful off the field.
A few Genshin Impact leaks have stated that Yelan is expected to make her playable debut in the 2.7 update. It hasn't been confirmed yet, but if it did happen, that would make her release date either:
Some [Questionable] leaks have been wrong in the past, so Travelers should keep that in mind. Some of them
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