Finger in mouth

Selina

My almost 1 year old daughter has a habit of putting her index finger in her mouth till the point where she gags! She's also thrown up multiple times from doing that!

When we see it, we pull her finger out and tell her no... but we've also lightly tapped her hand. When we do this, she stops but only momentarily.

I need ideas as to how we can break this habit!