Its very unsettling losing a loved one, and natural to want to retreat. It can feel safe hiding away in our 'caves', but over time it can also do us harm as we become more isolated. I'd say some fear would be totally normal, a new job can feel scary, at the moment your family represents safety.
I think there's a couple of ways you can approach this, for me I would imagine your nans words - what would she say to reassure you or build your confidence - and imagining she is watching over you go and do your best, make her proud
Also, break it down into steps so it's not as daunting, our imagination often runs away without us realising, before we've even got the job we're scaring ourselves about the people, first day/month! So think of it in stages - its just a chat to start. See how it goes. Its a brief trip out of the house, like a practice run. Good luck
xx