as she is standing at her cauldron making a potion

Marie: seems right?...

she would add one more potion, just a drop, POOF!!!..., she accidently inhaled the smoke chemicals, she coughs for a bit till regaining her composure

Marie: man. cough that must have been wrong?... cough

the affects of the chemicals begin to do its thing

Marie: h- huh!?...

she falls to her knees and then POOF, her breasts enlarges almost revealing them fully