Why does cosmo die in sonic x

Well you see. Super Sonic and Super Shadow was having a hard time with a dark oak, a Seed like plaent who was about to expole the universe. That's when Cosmo's mom tolded her that she can save them. Cosmo shattered her amulet and turned into a adult. Comso flew up to dark oak and fused with him. That is when Shadow and Sonic had a chance to use the sonic driver on Him. Sadly Tails had a hard time to blast his beloved.

Well that is how Cosmo died