How can I deel with unbearable grief and pain due to a lost loved one?

It may be tough, trust me I know. The way I got through an awful time like this, I talked to someone I trusted and maybe you could talk to someone who knew your Aunty. Just pour out your feelings and if your not comfortable with that I suggest an exercise:
Write a pretend letter to your Auntie (who is in a better place) and write down all your feelings. Then after you finish your letter get a balloon and attach the letter to that balloon. Let if fly away and know that your Auntie will find it. This will make you more reassured and I'm sure your Auntie would be proud of you.