.
We tend to regress the subordinate verb, though the present is usually possible if the fact or condition still obtains. In your examples, I think these would be OK:
She, knowing all that is going to happen to her, didn't say a word and stayed in the spot.-- It depends of course on whether the things that 'are going to happen' have already happened in the context.
Knowing how old she is, she refused to have a drink.-- Again possible, I suppose, if she is still the same age now, but the point is, how old she
was then.
But this one is not, because it seems to me she did not hit the car-- a past established fact:
Knowing she (X) is about to hit another car, she veered off and avoided the crash.