I second Portia's advice about making sure she gets enough exercise (although a lot of these types of daydreamers use exercise to improve the daydreaming which may be why she's swinging). Just watch whats going on, and maybe set some rules for daydreaming -give her a specific time that is just hers to do it- see if she can do it though. With my son I don't know if I could set rules for it, he would probably break them as it's a way he's coping with anxiety.
Also ZS is right on about addictiveness- there are a lot of adults on the web who are trying to figure out how to stop dreaming their lives away...
Also, the good news is that if you outgrew it, this may be completely developmental and she will learn to channel it just like you did. And cammom has some good points too.
I think I read that Nikola Tesla walked 8-10 miles a day. Wonder if he was using that to think up some of his ideas...
