The couple split in November over their conflicting work schedules, but were seen together again at Lowe's North London home the following month.
Fresh reports say that the pair enjoyed another secret meeting at her home recently, prompting an insider to comment that a reconciliation should not be ruled out.
"They were always so happy together, which is why everyone couldn't believe they broke up," the source told the Daily Express. "Suffice to say that it would be wrong to assume their relationship is over for ever."
Smith and Lowe first started dating back in April 2010.
They briefly split the following May, but reconciled one month later.