It is Gilda who dies at the end of the Rigoletto. This is because of the understanding between Sparafucile who is a hired killer and Rigoletto who is the father of Gilda. Gilda decided that she would sacrifice herself for the Duke.
She is fully aware of what would happen if she comes knocking at the door but she still decided to push through with it. She died because she was stabbed by the hired assassin. The body was then wrapped in a rug and was sent to Rigoletto. It was in the river when Rigoletto saw his daughter Gilda before Gilda truly died.
Gilda died at the end of Rigoletto. Sparafucile (a hired assassin) agrees to kill anyone who comes to his door to knock before midnight and if no one comes the Duke will die. Gilda sacrifice herself. She knocks on the door of Sparafucile and she was stabbed by Sparafucile.
Rigoletto (Gilda’s father) was the one that hired Sparafucile and he was planning to kill the Duke. Sparafucile wraps her body in a rug and drops it through a trap door to Rigoletto. Rigoletto paddles to the river to dispose the body only to unwrap to rug and discovers his almost dead daughter. Gilda eventually dies.