A poster from the Fuselage who knows Mira Furlan posted this.I know that this [Episode 11] is not a Danielle flashback episode, but I also know that "Danielle" is likely to be in it.
Mira is heading back to Hawaii to shoot a scene or two with Naveen very soon. She won't be in the episode a lot, but it is possible that this is a setup for future plot lines. She was originally supposed to have been there a few weeks earlier, but there was a scheduling conflict, so I'm not totally sure if she is in 10 or 11.
As for a potential flashback episode, I've seen Mira up close and personal many times, with the right makeup, it would be quite easy to make her look 16 or so years younger. Source: Zlanta@The Fuselage