Take it out shopping. Pay somebody YOU TRUST to steal it and burn it to its wheels.
If you don't have the kind of relationship where:
1. She didn't know better than to spend $150k on something you won't absolutely love
AND/OR
2. You can't be forthright with her about your feelings about a $150k gift.
Then the safest thing is to have it stolen and destroyed (they always find the fucking things, it needs to be destroyed).
You trade it in odds are her feelings will be hurt.