Rub your mouse over her stomach until you hear a burp. (About 5 seconds)
For me, this has been an issue on every episode. I did not realize it takes 5 seconds, as I think after 4 seconds of no feedback that something is working, I'd just try moving my mouse differently. After trying again with this knowledge, my issue seems to be either the countdown resets whenever your mouse leaves the hitbox, or the hitbox is much smaller than expected.
Video: https://drive.google.com/file/d/1nrwzIsz-tbVPVWI3StoxQL5FAXjiHZGi/view?usp=shari...