Jane can still pump air in party balloon even though it is already inflated. What explains this phenomenon?? ?

This phenomenon can be explained by the fact that the balloon is made of stretchy material, such as latex, which allows it to expand and contract as air is pumped in or released. Even though the balloon is already inflated, there is still some room for additional air to be pumped in, causing the balloon to expand further. However, there will be a limit to how much air the balloon can hold before it bursts.

Boyle's Law