She seems relatively coherent for somebody who is alleged to be so unwell. My aunt has schizophrenia and when she's in an episode of psychosis she posts and sends complete gobbledegook (delusions about god, the royal family trying to assassinate her etc).
I'm not convinced that FH is anywhere near that level of ill. Sure she probably has something going on upstairs, but nothing that should absolve her of accountability.
There will be hundreds of us on tattle who have various mental illnesses yet don't behave the way she does. She obviously has capacity.
Her posts make sense (aside from when she's trying to convince people that she didn't have any involvement with Richard then goes on to contradict herself) and she just comes across as a complete hole to me. A racist, homophobic bigot.