My girlfriend said that I was an inevitable robbery in her life. How should I answer her?

First of all, this is a very touching sentence, which expresses your importance and irreplaceable position in your girlfriend's life.

If you want to answer her, you can say this:

"Honey, I'm really touched to hear you say that. You are also an indispensable existence in my life, just like a light, guiding me and letting me understand the true meaning of life. No matter good times or bad times, I will always be with you and spend every disaster together, because there is nothing we can't face together. "

This answer expresses your gratitude and love for your girlfriend, and also shows your determination and confidence to face the future with her.