AceShowbiz - Nikki Sixx is struggling to accept his ex-girlfriend Kat Von D has found happiness with Jesse James - because the celebrity tattoo artist was declaring her love to the rocker just a few months ago. Von D was first linked to Sandra Bullock's former husband in August after revelers spotted the pair enjoying a night out in Las Vegas.

The inked-up couple went public with their relationship last week, on September 2, when they posed together for cameras at the opening of Von D's new Wonderland gallery in Hollywood, and she couldn't stop gushing about her new man. Von D told People, "Jesse is only my ninth boyfriend. I don't hang out with anybody unless I am in love." And when asked if she believed James was the one for her, she replied, "I believe he is, so yeah."

But the revelation has hit Sixx hard - because the Motley Crue bassist didn't expect her to fall in love so soon after their split earlier this year. He tells TMZ, "You know, it's hard when you (were) just told by someone you dated for two-and-a-half years that you're the love of their life... and then they move on so quickly." However, Sixx insists Von D is still an "amazing girl" and insists he wishes nothing but "the best" to his ex.