Your underlying issues have surfaced somewhat in your post, i'm really sorry about your loss and i hope Allah grants her Jannat.
You mentioned that your not close to your mum and also about how you hide your emotions, it seems that in your aunt you could show those emotions that seem to be bottled up in front of your immediate family.
Why can't you share your feelings with your mum? do you have any sisters that you can talk to?
Grief is a very personal emotion, there is no right or wrong way to handle it, some people take years (others never) to get over grief.
Get closer to your deen, i know you may have heard this before, but honestly the closer you to religion the easier it is to manage, namaz, dua, Quran it all eases the pain.