Could someone please give me advice on how not to hate my stepdaughter?

The reasoning for me feeling this way is due to the fact that she lived under my roof for almost two years and she never once thanked me for cooking for her, cleaning everywhere in the house but her room (i even cleaned up her just dastardly filth of a restroom). I even would stand up and iron her clothes for her just so she could wear them the next day. She has taken such advantage of her father due to his service in the military and since his divorce from her mom that she stated she hated until our marriage has been on egg shells. She would put trash down not even a foot from the trash can and would expect me to pick it up and trash it for here and she had places in her bedroom for her school books but they could never seem to get to her room, this is to include dirty socks and other miscellaneous items. Her room stunk and so i had to clean everyday in other parts of the house to keep the smell confined to her room so that if someone came over they did not get a wiff of that stinch. Then one day I bought some cokes and was told company was coming and i did not want all the drinks to be drunk up due to the fact they had to last until next payday. She then went in to my bedroom and was snooping and found the sodas. That very evening she went on facebook and stated such mean things of me and some of the replies that came back were just gastly cruel and could cause me much harm. I told my spouse (her dad) and he just giggled a little bit but then i stated he had better straighten her out or I was leaving. So my family found this stuff as well and of course they were not going to let her do that to me without having something to say back. So when this started his exwife decided to say that i was a psycho b!#** (this woman has never met or laid eyes on me to call me this). So then i came down to he needed to fix this or we were in the past. He then told her that she had better apologize or she would get a repremand like a 12 year old OH YEAH this person IS A 26 YEAR OLD living under my roof with no job or no income at all and us having to foot all her bills and I had to put up with all that mess with her. Anyway he told her she had better say sorry . She then looked at him and stated that she would never say that she was sorry for any of the hurtful things or ways that she disrespected me in my home. I even had went as far as to let the dogs (big as horses) go into her room and sleep at night. (that’s why her room stunk she never cleaned or nothing in there even when they decided to pee and poop in there. Well, when her dad told her to say that and she stated what she did; that afternoon when he got home she moved out.