I agree she needs prep event before YEC but just before YEC i'm not sure this is good idea, see how new haven - uso worked out, also i think it would threw off her actual preparation and work on errors if she does any. only if she can play thursday and friday there just to get feel for her game
New Haven to US Open was a little different, cause Petra was going on 5 straight weeks of tennis--during the summer--if she had beat Bartoli.
This is a little different. Petra hasn't played much (as Holdworth noted), and she's had time off as well.
Luxemburg probably wouldn't bother her (because of those reasons). And Vika played Luxemberg last year, and still made the finals--playing Petra.
You would prefer the week off before. But it probably wouldn't make much difference in her case.
As far as "throwing off her practice": Petra actually left Kotyza home (she didn't even plan on going to Linz, and made up her mind at the last minute), and used Linz as a prep/practice venue for the YEC (and trust me, you could tell), till she worked her way into that brilliant all court game and won the tournament.