Right off the bat you describe her as always having been sassy, and yet in the same sentence you say she is just now becoming hateful and disrespectful. Not to put too fine a point on it, but which one is it? Has she always been sassy or not? Because "sassy" is just a euphemism for a lot of people for saying, "She's so cute when she acts like a disrespectful brat so we're going to ignore it and not discipline her."
So. It sounds like there's a lot of talking AT her instead of with her. It also sounds like she's being allowed to blame others for her own behavior. Neither is cool or acceptable.
It's time for her to have consequences every time you get a report from school, and every time she does these behaviors at home as well. No more of this, "But honey, whyyyy are you doing this? You have to stop, mmmkay? You have to stop because _____." It's past all of that. She knows she has to stop, and she knows why. Because it's disrespectful and rude, and better behavior is expected of her. She's not a baby any more.
If this is her trying to get attention, she won't be able to tell you that. Just assume it. Spend more one on one attention with her, give her more positive reinforcement and natural consequences as well as consequences that she can count on (establish house rules with set and clear consequences). For instance:
1. We tell the truth in this house. For every lie, the consequence is _____ <---negative thing here, like an extra chore
2. We respect teachers at all times. If a teacher is disrespected, the consequence is _____.
3. We respect parents at all times. If a parent is disrespected, the consequence is _____ <--- loss of a specific privilege.
Keep going with house rules for cussing, messes, chores, and other behaviors that need to be addressed. Keep the language as positive as possible with clear cut consequences. That way if any of the children break the rules, they can be applied evenly and fairly AND you don't have to think up a punishment on the spur of the moment.
Also have a reward system so that good and excellent behavior is rewarded with something meaningful, like extra one on one time with Mom or Dad. Or she gets to choose the weekend family activity that weekend. You need positive motivation for her, not just punishment, in order to discipline her. She needs to want to behave well in order to get positive attention. Behaving well has to be more beneficial than behaving badly.