LiLo and SamRo encounter an unwelcome presence from Lohan's past, and somehow escape unscathed.

Pretty much everyone was hoping to catch Samantha Ronson's DJ set at London nightspot Chinawhite last night—including Lindsay Lohan's former beau and cocaine aficionado Calum Best.

The Daily Mail reports that the nightclub was mobbed by hundreds of fans and photographers as Ronson's set loomed. Among the throng was Best, 27, who was intent on saying hello to his former flame and her new love.

However, an insider reveals, "Lindsay was horrified when she found out Calum was there and refused to talk to him. Samantha gets jealous of her former male lovers, and Lindsay didn't want to upset her."

Plus, things have tended to get a little sloppy for Linds, 22, when she runs into Best in nightclubs.

Even so, given the fact that Best was the one who turned Lindsay toward female companionship (or so he claims), Ronson, 31, might have at least wanted to offer him her heartfelt thanks.

Still, it can't be easy for Lindsay to avoid her substantial romantic past and get on with her life.

It's enough to drive a girl crazy.