Oh that's a tough call.
As a parent myself, you did what I probably would have done. (Actually, what I would have done would probably have been worse.
) From the sounds of it
someone needed to say
something. Your child is your child and you have an insinct to protect them no matter how old they are. (My mom is this way.)
On the other hand, she's 19...barely and adult legally, but still, an adult. You stepped in and interfered against her wishes. Especially considering her persepective of the situation--at that age, I had parents who stepped in and tried to control situations when it wasn't their place. It's like you are doubting her ability and judgement. Even if she does appreciate and understand later in life why you did what you did, I think she's totally justified in being really po'd with you.
I can see and understand both sides.