My orthodox cultist vegan coworker refuses to own pets, and refuses to walk on grass out of fear of crushing bugs, is she mentally sick?
I don't know. I know someone like that. It seemed to get more severe over time. At first it was just the vegan diet now it's very similar to what you have described.
Veganism is technically a mental illness, i.e. schizophrenia that is loss of touch with reality. Such extremist groups as PETA and ALF cause mental illness.
Probably not mentally sick, just an extremist, veganism taken to the extreme, compare with communism [extreme socialism] or fundamentalism [extreme religion].
She's vegan.. That is a mental illness all of its own
whats it got to do with you
That sounds atypical and odd, but not mentally sick - though it might be a manifestation of a mental health issue.
she is what she is. Ignore. Its better for YOUR mental health.
Curious... would she try to slap and kill a bug, that just stung her?
Being vegan is a choice that offers many rewards to those that follow the principles. As with any association, you can take things a bit too far. Most of all it doesn't seem as if this person is hurting anyone. So if it works for her so be it. I don't see anything that falls into categorical illness.