Leftover can refer to money as well?

I'm familiar with the word 'leftover' which means food remaining after a meal.

Well, can it also refer to money?

While talking about what we would do if we won the lottery
and got one million bucks, my friend said,

"I will buy a car. And if someone asks me how I would do with the leftovers, I will donate people who need help."

What she meant by 'leftovers' there is, she said, money remaining after spending on the car. Can the word 'leftover' be used that way?

And her sentence seems a bit unnatural from my point of view, and this is my version of re-writing it.

"I will buy a car. And if someone asks me WHAT I would do with the leftover, I will donate THE MONEY to people who need help."

My guess was

1. 'what I would do' is a better one than 'how I would do'
2. If leftover can indicate some money, it should be a
singular form as money is uncountable, and, lastly,
3. Native speakers don't seem to say 'donate someone', but 'donate something to someone'.

Would you please take a look
and help me learn better phrases?

Thank you very much.