Her bosom is certainly ample. Generous, even. But not colossal. She is well-proportioned, and I have not the slightest fear her spine will snap.
It also looks like a bosom, rather than two captive balloons glued to her chest. They're shaped like natural breasts! And they look as if they'd squish rather than pop if you prodded them. I can't even see nipples forcing their way through her costume! THIS WILL NEVER CATCH ON.