Sienna Miller and James Franco

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Just when you think Sienna Miller and Jude Law are back together for good, rumours start swirling that she's macking on another guy. And according to TMZ, that guy is none other than Sienna Miller's co-star in Camille, and Spider-Man's Harry Osbourne, James Franco.

Sources tell TMZ that Miller is on to her next leading man, James Franco. The two are currently filming "Camille," a movie about two honeymooners' road trip to Niagara Falls. The pair were spotted this weekend in Toronto getting cozy after-hours.

During filming Friday afternoon, the leading pair had to roll around the hay kissing as Franco's shirt was off. Once the set wrapped, sources say the couple took the on-set frolicking off-set, well into the evening. The two took in a concert and were seen canoodling and dancing in the streets together. Around midnight, Miller and Franco got some Chinese food, enjoyed a cigarette together and hit the nightclubs.

Man that girl moves fast. Kinda gives you hope, doesn't it. At least if you're one of the best looking men in the world. So does this mean we've seen the last of Sienna and Jude Law? Well, I wouldn't bet on it. But don't feel too bad for him. He's probably off screwing the nanny at this very moment.