Hi K.!
First, you need to know, that this is normal girl behavior. It can last for about 2-3 years!!!! Hopefully not that long, though.
At first, we went through "shock", and not knowing how to respond. Then , we tried to react "properly" with a calm tone saying, "honey you are surprising me with this new attitude you have........can you please relax..." Obviously, this was a way too "mature" approach for her, because it was too nice and created more sarcastic responses from.
When the un-appreciation began, I stop doing her laundry and breakfast, etc... It was up to her, the "New Enlightened One with all the answers"........oh boy, did that create a "Cinderella" mode, but at least I wasn't doing anything to be yelled at for.
What started to work, was when she actually NEEDED me for help (a ride, or something). Then my response wasn't... well, lets' just say my responses were something I wasn't too proud of then :o) But I was at the end of my rope! If she needed a ride, I would remind her of all the hurtful things she has said to me that day, like "Oh, you mean, the ugly skirt mother, who makes runny eggs and doesn't wear her makeup right?...excuse me...did you say you needed something from me?" The first time I said that, she was shocked because I finally lowered myself to her level/age.
Anyway, when it got really bad....I phoned) her cheerleading coach (in front of her), and told the Coach that my daughter's attitude has broken the boundaries of family values and respect. I told the Coach that there might be days when my daughter isn't at practice because she disrespected me and I will refuse to take her..... That opened her eyes because it hit at her heart.
Unfortunately, it took me lowering myself to her immature level with sacastic replies back to her. Something that I'd worked years to overcome in the first-place!
K., just know you are not alone. Stand you ground of respect early on, and she will learn faster than my daughter. I gave my daughter too many chances because I was trying "to be nice". Show you daughter that you mean business. You might have to ask your younger daughter to leave the room before you 'speak"....
Good Luck!
~N. :o)