Does this means she's vegan/vegetarian?

She probably is unless any of the other adepti have given her a meat based dish. I think I recall Shenhe saying something about eating flowers so maybe the same applies to Xianyun as well

she only eats the guilty ones

Xianyun special recipe are meatballs
the base recipe is meatballs, the special dish description says meatballs
so there is no alternative used instead

Who's to say the animals she may or may have not slain are actually innocent?

the only known vegan is Ganyu (her actual lore only says vegetarian)
who, besides not eating meat,
we had info about refusing food that contains milk or eggs
which i think is from the event where you could actually give food to characters

Well if we're being technical, eating meat is not the same as "taking an innocent life". Someone else did the butchering.

It operates on the same logic as "All life is Sacred." This doesn't exclude you from eating meat, as eating is seen as a form of honoring the life of the animal.

She Is Crane do you know what Cranes eat?

Calling this a stretch is an understatement. The distance between *"I have never taken a life"* and *"I have never eaten meat"* is like from Amsterdam to Baghdad. Not to mention that, while she's not an animal per se, cranes do indeed eat meat.

Not according to the Sweet Madames I feed her, no.