Disclaimer: I'm gonna be honest and rough, I'll look at death scientifically. Don't read it if you think you're not ready to hear "rough" facts about life.

Well, life is hard. Humans are too smart to accept death as a simple natural occasion that happens to 90% of living creatures (some animals are immortal), that's the exact reason humans made up religion, that's the the exact reason they made up a god to help them cope with their problems in life (of course that god doesn't do anything, it's all about the mental support.

But of course humans have a purpose. All living creatures have one. I think our purpose is learning more about our universe. Nothing is really going to happen to us after "death", your atoms and molecules will simply be reused in nature . It'll be used in creating new creatures , or chemical compounds. Humans simply feel alive because of their brain , there are some animals that don't feel themselves, they don't know they're alive, because their brain doesn't have as much self consciousness as we have. And this self consciousness has made it hard for some humans to accept death as a fully normal occasion. If we don't want to die and then be reused then we should find a way to make ourselves immortal , because it's 100% possible, as I said some animals are immortals.

So ,Dad, don't worry. What gives life to humans is their actions, personality and the memories of them in our minds. As long as you have her in your mind, she's alive. She'll be living in you rent free.

Don't take it hard on yourself. Accept it. Maybe she didn't like this world. Maybe she didn't wanna live a boring life like most other humans. She's now freed from all that.