It can be either one, depending on your meaning. You would "respond to" a question or comment directed at you. You would "respond for" someone else who cannot respond for themselves.
Quelqu'un va venir. (Someone is coming).
Your welcome.
My pleasure
I am looking for an attorney to help you. Someone will respond as soon as we find someone.
RESPOND: To answer or react to something. For example, When someone calls your name you RESPOND by looking to see who called you. Or you RESPOND verbally by saying "I am here!". When someone writes you a letter you RESPOND by sending a letter back to them.
Its all right
Good
no you didnt
Banana
You are kind
You can respond with a simple "Thank you for your sympathy" or "I appreciate your concern."