My Fancy Rat died today?

So I'm a very affectionate person when it comes to animals. My brother had 2 fancy rats since December and basically we really loved them. Today when I woke up she looked ill. Long story short she died and the other one is fine. I just can't seem to get over her death. She was so small and cute and for her to be healthy one day and the next die is just mind blowing. Like any other crazy pet person I cried all day and can't seem to get over it. So my question is has anybody had a rat die or a pet closest to you? How did you deal with it? Thank you