Is my dad's girlfriend normal?

My Dad's been with this woman for several years. She started off nice, but as time went on she became more nasty and vindictive. She scratched my laptop with a pen knife, got my sisters into trouble, picked fights with my Dad over tiny things when his blood pressure's already high...etc. Recently she's been worse than ever. She lost her job so sits at home all day on facebook and rarely cleans the house, yet she has the nerve to call everyone who isn't herself lazy. We went on holiday together and she spent the whole time putting everyone down. She called me stupid, lazy and mocked my attempts to learn her language (polish), she made fun of my little sister's illness (she's been ill for a while and no one knows what's wrong with her, but she often feels sick) and she complained in practically every resturant we went to. She complained about the clothes I bought because they weren't to her tastes. On Christmas eve she started a massive argument with my Dad because her 23 year old son didn't have a Christmas stocking. It got so bad that dad sent us to our mum's for Christmas.
Yesterday I told my Dad how I felt and he agreed with me. He wants to leave her, but doesn't want to kick her onto the streets. I'm at my mum's now and my dad's gf has been sending me bitchy messages from facebook, including hacking into my Dad's and younger sister's account.
Is she normal? :)
edit: forgot to mention she's chucked a wine bottle at my Dad, chucked a cutlery drawer across the kitchen and will go and wreck a room when she doesn't get her own way.
(sorry this is so long)