Hi guys!

I made the following mistake in my last class test, my sentence was:

Now, being free and emancipated it is down to her, she can decide.

In this case it apparently should have been "up to her", but I don't know why, because I'm pretty sure that I heard it before in a context like that. Anyway, could anyone explain to me why it has to be "up to" here? Maybe anyone can tell me the difference between "up to" and "down to" in general, too.

Many thanks in advance...
Idiomatic. To be up to (someone) = it is (someone's) right/responsibility to make the decision.

Down to needs more context before I can essay a definition.

Put our loss down to our incompetence.
It was down to the wire before a winner was finally chosen.
I'll be down to get you in a taxi, honey.
It's down to -20 degrees outside and I'm down to my last ten bucks

There are multiple uses of that collocation.

It's down to Tom. I've heard this expression in gritty British crime TV shows where they talk in a slang-y kind of way. The kind of context is:

A: Who robbed the bank?

B: It's down to Tom.

I think the idea is that it has been identified that Tom was responsible. Perhaps a gritty, slang-y British reader might care to comment?

Best wishes, Clive
Students: We have free audio pronunciation exercises.

Still remains vague. Is Tom a suspect, or police? Has a process (of elimination, for example) whittle the field down to Tom? Whether television or reality, the truly impressive speakers and writers eschew vague references.

Teachers: We supply a list of EFL job vacancies