How did didyme die and what was her power?

In Stephenie meyer's Twilight Saga it does not mention what Didyme of the volturi's power was or how she died... but i have the answer to how didyme died and what her power was here it is:

Aro got changed into a vampire and he wanted to change his younger sister Didyme into a vampire hoping she would have a good power that was very useful to the volturi so he changed Didyme. Didyme's vampire power was that she has an aura of happiness. (Her power would make people happy). Aro was not very impressed with her power. One of Aro's volturi clan mates, Marcus fell in love with Didyme... they were so happy together that they wanted to leave the volturi clan and live on their own. Aro was very mad that they planned on not being with the volturi anymore. So Aro killed his sister Didyme even though he loved her very much because her and Marcus were going to live on their own. Then Aro got Chelsea to use her power on Marcus to make him stay with the volturi. And that is what Didyme's power was and how she died.

p.s Chelsea's power is to make other vampire's want to join the volturi and to make other vampire's in the volturi clan to stay there.