Violet is learning how to whistle

Violet has wanted to figure out how to whistle for a very long time.  She usually pretends to whistle by singing with her lips pursed...but she knows it isn't actually whistling.  I was on the phone for awhile this afternoon  and Violet was laying on the couch looking really bored...but I wasn't paying much attention to her.  She suddenly sat up and said "MOM! I just whistled!" and she blew out of her mouth and at the end of her blow a whistle sound came out.  She practiced for a little longer and said "oh this takes too much practice!! I'm going to work on it tomorrow!"