Advice on niece who's mam has died?

My niece is 18 years old and has been through a lot in her life, her mam was an alcoholic when she was younger and she went to live with her dad for 7 years before moving back with her mam aged 16 after finishing school. In my opinion she was better off with her dad as her mam has never really been stable and I wasn't really sure why she went back to her mams in the first place as she doesn't talk about and as far as I know she hasn't kept in contact with her dad.

Her mam died nearly 7 weeks ago. She's staying with me but at college all day and wear helping her with selling her mams house and paying off the mortgage and debts. She has been coping so far and well and has been focusing on getting into university next year.

However there have been some things happening recently, she is sad a lot which is understandable but she got better for a while and then has started getting more down, tired etc. My wife says she still cries in the middle of the night but what's most worrying is that both my kids have heard her talking to herself, she says things like leave me alone, I'm sorry, and they say it sounds like she's shouting back to someone who is shouting at her and she gets really upset over it. She's not been herself, even after her mother died yeah of course she was upset but in he last couple of weeks she's been acting very odd and not herself. I'm worried that is could be something more serious, there's a lot of history of mental health in our family me I fear she's

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