Hi and welcome to the forum.
I agree - free roaming is not a good idea.
Bengals have no road sense - as they are a relatively new breed, they haven't learnt how to adjust to the cars on our roads, unlike the good ol' moggy, who, over time, has adapted itself to be a little streetwise.
I recently lost a beloved Bengal boy to the road and i will never, ever go through that again.
My two are now indoor cats, who are waiting for their outdoor run to be built.
It won't be huge as we don't have much space to play with, but it will be a little, safe, haven for them both.
I would suggest that you build some kind of enclosed run that attaches to your house, depending on your garden, of course. It sounds like Mini is protesting at being kept in.
It might be worth getting her checked out by your vets just to be sure that nothing else is bothering her?
I hope you get some peace soon! x