I agree with your friend. It is redundant to write "discuss about." The definition of "discuss" is "talk about;" so, when you write "discuss about," substituting the definition of "discuss," you're saying "talk about about." Other than redundancy consider this; the 1st use of "about" is an adverb which is how I think you are using it, and as such it could be used to modify the verb "discuss," but "about" used as an adverb means "almost" or "nearly." Think about it; are you "almost" or "nearly" discussing something?
An alternative use of "about" is as a preposition. If to write or to say ". . . discuss the . . . " as your friend suggests is uncomfortable for you i.e. it doesn't roll off the tongue as if something is missing, you might want to use the noun form of the word "discuss," and reconstruct your sentence to read " . . . discussion on the. . . " or ". . . discussion about the . . . " where the prepositional phrase beginning with "on" or "about" offers you the chance to describe topic of the discussion [and is easier on your tongue and ears.]
There are two sources I consult want when I'm not sure of something. They are merriam-webster.com and dictionary.com which offers a free app for your Phone or Pad and a very moderately priced version without advertisements. In both; the free versions cover most of the grammar/spelling questions most of us have.
I hope I've helped.