My question involves restraining orders in the State of: California

I live in a four plex and my girlfriends mother lives two doors down. her daughter (my girlfriends sister ) is a harassing manipulative wretch and wont leave us alone. she uses indecent text messages to harass Judy daily sometimes fifteen times. she comes to my door and bangs as loud as she can and because the hatred is there we don't answer it. Judy my girlfriends mother is in the hospital and her sister is cleaning out her belongings saying she is just taking what mom asks for but she is taking everything and we need to keep her off the property at least until her mother either lives and comes home or passes on and we do what her mom wishes. not take everything for her self the real problem is her constant harrassing ways she use. I told her to stay away from my house and she ignores me, and continues to bang on the door and scare Judy. Judy feels trapped in her house and cant get free from her sisters evil attitude. I have to admit she is a mean witch with no consience for others feelings . She is a sociopath and it is very apparent. please tell me if I can get a restraining order against her based on harassment and threats. We have kept every text she has sent and some are vicious and she even left notes on paper for Judy to find. please help.