I don't think it is such a bad idea. Maybe her confidence is a little low after some losses this past weeks and she wants to go into the French Open with a nice tournament title.
I've never understood why people don't like when top players play the lower-ranked events. I mean, Sharapova did it in 2004 and everybody was on her case. I think, that if you want to win a tournament and some matches before big events, why not.
It is good for the WTA to have top players playing everywhere.