De versus sobre

Question

I don't understand how to determine when to use "de" versus "sobre" for the word "about". Las chicas están hablando de mí >> about --> de

Yo soy honesto. No puedo decir lo mismo sobre ti. >> about -->sobre

Thank you.

Accepted Answer

Hola Rosemary,
I use them interchangeably and it seems to be fine with my (native) Spanish language teacher.
Don’t take this as cast in stone, but I think “de” is generally favoured with hablar. Hablar + de translates as “to speak of.” Thus “La vieja hablaba de una época cuando …” (the old woman spoke of a time when …...). In English it sounds quite poetic or wistful, but it still makes sense, and to translate it as “about” is more modern. The  Kwiziq teachers may well be able to expand on this. 
Saludos. John

Answer

Thank you, John.