Try to talk to her. Make her understand that everything that is yours is ultimately hers too. So, she doesn’t need to be worried about it. She shouldn’t be so vicious to your parents. Poisoning your parents means she tried to kill them.
If you want to take legal action, then you can file an F.I.R under Section 307 in The Indian Penal Code.

Section 307(Attempt to murder) states – Whoever does any act with such intention or knowledge, and under such circumstances that, if he by that act caused death, he would be guilty of murder, shall be punished with imprisonment of either description for a term which may extend to ten years, and shall also be liable to fine; and if hurt is caused to any person by such act, the offender shall be liable either to imprisonment for life, or other punishment according to the law.