About the time you start treating your 19 year old the way she is treating you - her feelings would be hurt and she'd be plenty upset.
She's one to two years out of high school. And doing poorly in college is not an option.
Sounds like she needs to get some concrete plans for herself and her life. She's not a kid.
She is old enough to have a job and have her own apartment. Maybe that is what she needs to do until she can decide what she wants to do with her life.
And Shanna K - disrespecting your parents is not a "phase" and not "normal". It's wrong, a sin, and shows a lack of understanding and concern for the people who love you the most and want the best for you.
Some 19 year olds just need a good old fashion whupping.