Ok so coming back to look at this now it looks like an odd post but I think the fact that I would even ask this question says something about how peeved I was at the time.
How do you force someone to think for themselves?

Another, less pissed off example.

She wants to buy a house.

I want to wait till around the end of the year.
Our collective credit scores are going up(I have a student loan coming out of default among other things)
We are borderline subprime (680) and there is all kinds of turmoil in that area right now.
I think the stock market is headed for a correction, moderate economic downturn.
That will be even better for buyers.

She understands none of this. All she knows is that she wants a house.

I try to explain these things and it's like telling your two year old in detail about how many bills you have and why daddy can't buy a $200 Power wheels.
(ok feeling a little guilty about my last razor now)

They stand and stare and then throw a tantrum. I WANT I WANT I WANT!!

Should I make her stand in the corner? Time out?