Who and whom
I saw the woman whom you said lived next door.
I saw the woman (who) you said lived next door.
We rarely use whom in modern English. We still use it after prepositions to, by, with, after, on etc. For example. The girl to whom you were speaking is Nigerian, We prefer to avoid this now a days by changing the order of the sentence: The girl you were speaking to is Nigerian. You can also use that in place of who: The girl that you were speaking to is Nigerian.