It's entirely Dan's private life and his choice. I don't know why and what, but there's something about Erin that makes me not like her :P (not 'cause she's been dating with Dan). By contrast, I took to Rosie ;P

Yes,Its Dan's own life,he can date anyone he loves! But Idk why I dislike Erin :/ even Rosie! I wish dan find an awesome life partner who never betrays him becz betraying became a fashion in hollywood! & I want him to be always happy!

Hell no. Because I can see right through Erin's innocent girl act.
And she's not even that innocent as she seems. And people may
think that she's a great actress, but she's just as terrible at acting
as Kristen Stewart, even though I love her in Speak and
The Runaways. And I don't care if Daniel is happy. He should
know that this idiotic woman is just using him for money
and fame.

He can do what he likes but she doesn't seem to really treat him great. She's a terrible actress and really ugly. I fail to see what he saw in her. Not a great carrera at all and less so outside the US. Dan is the one making her special. Anyways that says a Lot about Daniel's selfsteem and faith in life.