PHOTOSYNTHESIS: Ur doin it wrong
The science in this is all wrong.
Plants take in CO2 and emit oxygen when performing photosynthesis, the process by which they create sugars. When plants metabolize those sugars for energy, they respire, taking in oxygen and emitting CO2 just like animals do. Indoors, Ivy would perform more respiration than photosynthesis as artificial light is a poor substitute for sunlight. (You need special lamps to properly sun plants indoors.) She would actually last longer in a sealed room than a human, to an extent in direct proportion to the power of illumination.