Sienna Miller, who has earned more headlines for her love life than for her acting, might be dating Josh Hartnett. There were rumors that she and Balthazar Getty (who is still married to his wife Rosetta), broke up in January, but last we saw they were seen kissing at the airport in February. Balthazar and Rosetta are said to be estranged, but trying to make it work for the sake of their four children.

Now it seems like the relationship between Sienna and Balthazar is totally over, and the Daily Mirror is reporting that she is now seeing Josh Hartnett.

A pal reveals: “Sienna loved being with Balthazar but there was too much baggage and she couldn’t commit to anything more than a few months. They are still good friends.”

The pair began dating after they were introduced by Sienna’s Edge of Love co-star (and former beau) Matthew Rhys last May while Balthazar was nursing a new baby with then- wife Rosetta.

Now Sienna is getting more and more friendly with Hollywood hunk Josh Hartnett. My moles tell me she flew to his bedside in New York when he got a bad tummy bug and nursed him back to health – and they chat all the time on the phone.

My source reveals: “Josh and Sienna have a unique bond. They understand each other and I wouldn’t be surprised if a relationship blossomed.”

Sienna’s aides will be thrilled by the break with Balthazar. The relationship led to her being branded a home-wrecker and is rumoured to have put an end to her role as Maid Marian in the new Robin Hood movie. The source adds: “She has a real chance of hitting the big time again.”

But it’s not as if she needs that much help. The talented blonde is preparing for the release of GI Joe where she’s a leather-clad villain. Sienna tells me: “It’s going to be big for me. Then I’m off to Broadway, treading the boards.”

[from The Daily Mirror]

Of course this is the Daily Mirror, so take the Josh Hartnett bit with a grain of salt. But maybe Sienna has finally realized that openly dating a married man and being photographed topless with him was not a good idea. This isn’t the first story we’ve heard about Sienna and Josh hooking up. They were also linked in the fall of last year, when they were spotted on at least two dates.

As we’ve reported, and as mentioned in the article, Sienna’s reputation has been ruining her chances for roles. The official story was that Sienna was “too young” to play Maid Marian to Russell Crowe’s Robin Hood, and was replaced by Cate Blanchett. But it also seems likely that her diva ways and self-entitlement didn’t help either.

The last we heard from Sienna she was in the Congo reporting on the beautiful surroundings and luxury hotels.

Josh Hartnett is shown on 4/15/09. Sienna Miller is shown on 5/18/09. Credit: WENN.com