Anna loves to bring her friends down. = make them sad or depressed by saying negative things which do not have to do with them personally though they could.
Anna loves to put her friends down. = say nasty/bad things about them personally which could cause others to feel that they are not good people.
I've never heard 'do' used this way though it could be a new slang term for some age groups or a dialectal difference.
put/do her friends down[/COLOR].
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