Suck it up

Grandma has a foolproof way to teach babies to drink from a straw.
She starts by putting the straw in the drink and putting her finger on the other end, then pulling some liquid out. The straw goes in the baby's mouth and she releases the liquid.
She does this a few times and then she doesn't release, forcing the baby to suck on the straw. Eventually, the baby learns to suck liquid up the straw.
Big sister got this trick pretty quickly, but we didn't think Little sister would ever get there. We've been trying for several months to teach her. She just couldn't get it.
Big sister was the one who succeeded, though it wasn't for really trying. It was out of sheer jealousy. Being recently weaned off the bottle, Little Sister was finally noticing that Big Sister's cups are different. Rather than sippies, Big sister uses cups with straws.
She watched and watched and would pick up Big sister's cups when she wasn't looking, only to get yelled out later -- "sis! I told you to leave my cups alone!"
This is normally followed by Stephanie or I lugging in towels or the mop to clean up the drink off the floor.
Something finally clicked the other day, and Little Sister just started doing it.
I heard a scream from the kitchen, but as I ran from the back of the house I could tell it was a fun scream because it was followed by giggles.
I came in to see Little sister taking a long drink out of a cup with a straw.
She grows up so fast, I wonder what's next.