Time to start charging her rent
Seriously, the mouthiness and disrespect are unacceptable. From anyone, at any age, but particularly from one's child. Totally out of bounds. ("Therapy session" -- how rude and disrespectful is that??)
Sit her down -- or, if she won't sit and talk with you, or if you feel it is too hard to talk with her about this, write it. First off, that you love her and want the best for her, and that includes her learning how to treat others with respect. Set out your rules for her to enjoy the PRIVILEGE of living in your house. Make it a clear and to the point list. Include behaviors (treating you with respect, etc), household obligations (chores and the like), any financial expectations (rent? Paying for her own clothes? Paying her own car insurance, gas,etc).
I work with college students, and I have a middle schooler. I do not put up with behavior like your daughter's, ever. And it has not hurt my relationship with my child, or with my students, either. My son and I are close, and I have a longstanding rep for being super helpful and totally take-no-crap with students. You needn't be as hard edged as me , but I do think you can and should take a firm stand on this.
If you can't do it for yourself, do it for your daughter -- if she does not learn to treat others more respectfully, she is going to have a rough go with others in the future.
Hugs -- none of this is easy!