You are so welcome here and I'm really glad you've reached out to get some support during this time.
From everything that you have going on at the moment - full time work, full time uni, final exams and assessmemts, being verbally abused and coming up to the first anniversary of your Mum's passing - it is perfectly understandable to not want to go out and socialise, talk to people and to find it hard to be motivated.
I think you should honour these feelings, and pare everything down to only doing the absolute essentials.
So I guess one of these eseentials would be your exam tomorrow. Could you forget about everything else today except for a) taking care of yourself (eg. nutritious meals, a bit of physical movement, plenty of water, and early night) and b) preparing for the exam/completing the exam.
Then once that's done, deal with the next essential (maybe an upcoming assessment?).
Remembering/honouring your Mum and this difficult anniversary is important and is definitely an essential, so maybe you could think if some loving ways to send love into the universe in memory of your Mum. Plant a tree? Go for a picnic? Donate to a charity? Light a candle and make her favourite dinner? Sit and send live to her spirit?
Do not stress about going out with friends or talking to people - there is plenty if time for that at another time. If you felt you needed to, you could message them saying you're having a really rough couple of weeks and need some downtime?
I am worried to hear about the abuse at your work and that you are too frightened to return. Do you have support there in the form of other colleagues or an HR department or other place you could seek help?
I hope you feel welcome and cared for here, you can come and talk any time during the difficult few weeks ahead, and any other time as well.