OP, i am concerned too, your daughter's behavior is indeed worrysome. At 19 years old, she should be emerging out of her teenager's years, making it unlikely that this would only be a hormonal thing. At best, she is going through some emotional and trying times and it affects her mood. At worst, something much more serious might be going on, but she is not feeling safe enough to share it with you.
Things that might be going on: she could have fallen pregnant in college before she dropped, she might be suffering from a depression or living a first romantic breakout, she may have discovered a different sexual orientation... It's hard to guess with the little information we have so far. But it would be safer to take it seriously.
The fact you wrote here shows you are conscious of this and are worried. Yet i have the impression that she doesn't preceive you as worried, so much as blaming (hence jer perceiving that you don't care).
When she acts out (smashing the dishes, etc) what she is doing is sending a message. She is saying: "i am suffering". If you react to the behavior rather than the emotion ("you can't do this in front of clients!"), she will receive it as a blame and feel that you don't understand her or don't care about her problems. Next times she acts out, no matter how bad the behavior, you have golden opportunities to show her you can ignore the behavior and express your worries and care: "awww sweetheart... are you okay? You seem to have a heart time... You know you can talk to me about anything right? What's going on?" ...it's not so much the words that matters: it's how you focus on her emotions and feelings rather than focus on the bad behavior. This will show her you care and open the door to lostening to her.
The goal is for her to realize that: there is nothing she can tell you that would make you love her less. Her hapiness is much more important to you than anything else, including judging her. She needs to feel, in her heart, that whatever she is going through, she can go through it together with you, safely.
It's your job to create the proper safe environment for her to realize this.
Singledad's advice about using active listening is excellent in that regards.
It's a powerful (but difficult!) skill to acquire.
Can you provide more context: does she has a bf or gf (romantic relationship)? How happy was she in her studies before dropping out? Does she know her career choices / passions / interests? Have you ever discussed her future? Did she had plans to leave the nest? Does she has any special needs or known conditions? Does she live home with you? What about the other parent? Siblings? Family?
