well, it simply means "to come to terms with"
"terms" means an agreement (as in, say, a contract)
Say your Uncle and you really hate each other. But, you have to share a house.
You would have to reach some sort of "working agreement" on how to handle that situtaion -- you both hate each other, but, you have to at least be civil, say, and not try to use the fridge at the same time, and you don't touch his train set and he doesn't touch your nintendo. A sort of detente, you know?
Another almost identical phrase is "came to an understanding".
"We had to share the house, so we had to come to terms with each other."
Note that he phrase is usually used in that sense .. two parties who hate each other, form a detente, an understanding, to get by without being at each other's throats.
However, it can also very simply be used in the sense of a contract or other agreement. How's your payment negotiation going? No problem, we came to terms.
in your particular example, it means has come to an "agreement" with Death.
So, as Erik points out, you are actually "dealing with" ("dealing" means "doing business with") Death.
before you "come to terms" with Death, you are perhaps still in pure shock, or perhaps in denial ("I can't believe person X is dead.."). you are behaving perhaps erratically, not looking after yourself, not eating etc.
once you start "dealing" with Death, you accept person X is dead, you start making arrangements - even though your life has changed dramatically you find an arrangements to press on.