I have a slow learner cousin. She is 24yo, but still, act like a child.

I was told by my aunt to take care of her last week for 1 days (Only about 8 hours).
I thought it is simple. Basically just keep an eye on her. That all.

However, I face difficulty to get along with her for that 8 hours. I really don't know what I had done to her.. she ends up even more depressed with me
I swear I will not do this kind of task anymore

Just wondering does there has any professional caregiver can go house to house to take care of this group of people?