The `Bleeding Love` singer and Lou - who met when they were just 10 - decided to call it quits after Leona`s busy work schedule stopped them from being able to spend any quality time together.
A friend told Britain`s Sunday Mirror newspaper: "Things have been under pressure for ages between them and they`ve finally realised that things are not going to be able to progress.
"Leona`s schedule means she`s in the States a lot when Lou`s in London and then when he goes out she`s over here. Then there`s the fact she`s been totally immersed in preparing for her tour. They`ve barely spend any time together whatsoever."
The final straw is believed to have come on Wednesday (16.06.10) when Lou didn`t turn up to see Leona perform at London`s O2 Arena, despite living just down the road in Hackney.
The source added: "Not showing up on Wednesday was the final straw. She`ll always treasure her time with Lou but she knows it`s a relationship that`s seen better times."