The Twilight hunk split from Garth in March (12) after 11 years of marriage, and he recently began dating brunette beauty Alexander, his co-star in TV drama Nurse Jackie.
Former Beverly Hills, 90210 regular Garth admits it is tough to watch Facinelli move on to another woman, even though she is quietly dating too.
She tells People.com, "I think there will come a time when it won't sting so bad. But I'm not quite there yet."
Garth and Facinelli share custody of their three daughters Luca, Lola and Fiona.