[Aw, almost had it. Admittedly Rudy can't help but chuckle at that.]

Ah, well... it's a bit hard to get used to at first. But you almost had it there, I think! When you whistle, try doing it a little more softly. And maybe shape your lips like this?

[As an example Rudy whistles again, lips shaped slightly different than before. Gently this time, and just holding one note for now. Trying to whistle songs right off might be a bit harder for Eley, so let's not do that for now.]