Thus, the question I have is if Catelyn went out of her way to mistreat Jon in the past -- and which form this might have taken -- or if she rather tried to avoid and ignore him?
"Mistreatment" is a loaded word. Did Catelyn beat Jon bloody? No. Did she distance herself from him? Yes. Did she verbally abuse and attack him? No. (The instance in Bran's bedroom was obviously a very special case). But I am sure she was very protective of the rights of her own children, and in that sense always drew the line sharply between bastard and trueborn where issues like seating on the high table for the king's visit were at issue.
And Jon surely knew that she would have preferred to have him elsewhere.