According to The Sun, "Tess realised she still had feelings for her ex after splitting from him to date Harry and has apologised to him for her romance with the singer ... She was in London this week and met her ex straight away — they’ve been inseparable since."
Good for her.
As for Harry, he and his family are currently mourning the loss of his step father Robin Twist, who passed away on Tuesday, so, it's safe to say that a probably fake relationship isn't very important to him RN.
See how the rest of One Direction sent their love to Harry and his family here.