This question already has an answer here:
Take the sentence:
Who is the right person to turn to?
I'm not sure whether who or whom should be used in this position.
Sure, it's fine.
The best advice about the use of whom is
Here is the easy way to figure out which one is correct. If you answer the question (or substitute the statement) with 'he' and it makes sense, use 'who.' If 'him' makes sense, use 'whom.' 'Whom' and 'him' both have the letter m so that is how to remember that they go together.
"Whom did you ask?" "I asked him."
"Who answered the question?" "He answered the question."
"Whom is the right person to turn to?" "Him is the right person to turn to." => INCORRECT
"Who is the right person to turn to." "He is the right person to turn to." => CORRECT
I agree with the previous answers in that "whom" is mostly being phased out of regular usage, so I would go with using "who" in this type of sentence. Some further support for "who" over "whom" here is that you are using "who" as a subject (and "whom" is only objective). Here, as in many instances, "is" is a linking verb; it links the description ("the right person to talk to") to the subject ("who"), meaning that both parts, basically, serve the same grammatical function.
For example, if I were to say "I am Michelle," then "I" and "Michelle" are equivalent. The reason your example is a little trickier is due mostly to the fact that we switch word order around in sentence structure, and that's enough to throw anybody off!