From my point of view,

Telling someone that you dream of them is just another way of telling them you think of them very much before you sleep till he/she appears in your dream.

Or to be brief, YOU MISS THEM.

So if someone you love tells you they dream of you, just be emphatic and tell them that you miss them too instead of just remain silent then interpreting it the other way that causes them heartache.

Is that too much to ask for? 

Well, unless you don't then, DON'T.