Hrm... I don't have this particular toy, but there should be either some screws somewhere on her, or an obvious parting line they used to put her together. I assume she takes batteries; there might be something to start with in her battery box.
If there are no screws anywhere to be found (aside from the one that might hold the battery box cover on), then they probably made her in two halves and snapped them together upon assembly. If that's the case, you'll probably have to saw her apart using either a hand saw (
) or a roto-tool of some kind; otherwise, you won't get her taken apart without breaking the plastic somewhere.
I hope this helps.
Good luck!