
Well, as you have tried the nice approach........Let's be not so nice.
My Dalmatian was fine getting into the car until I had a cage put in the back, then he point blank refused to go in.
I made sure he had a tight enough collar on as to not come over his head threw a treat in the back and heaved him in by the collar. I kept the voice firm and just said don't be such a wimp and get in (more for myself then him, thinking about it :) )
It took a few attempts, with a bit of heaving by a second person at the back end to start with, but I found by sounding like I meant it and I wasn't going to be messed about worked. After about a week he didn't need the collar holding and now jumps in by himself.
He is just playing you up (they are good at that). Be firm and decisive and you will win.
I nearly posted last time, but I though I would see if the nicey, nicey approach worked first, unfortunately as I suspected it didn't.
Take no nonsense from her, just go for it.
Good Luck
Sandra