There's also the Houdini Stop. It's mainly so they don't get their arms out of the straps but it might help keep the straps in place even after she's undone the buckle. Baby shops sell them. Also eBay.
Pregnant for the first-time?
Not sure where to start? We can help!
Our Insider Programs for pregnancy first-timers will lead you step-by-step through the 14 Pregnancy Must Dos!