Hello @Loyaltyzfynest
A very warm welcome to the forums, it is nice to meet you 
It is such a difficult thing when someone is not coping well but refuses to engage in help for it. They are lucky to have your encouragement and support, but that can burn you out easily, so it is helpful you have come to the forums for some support for this.
The best thing we can do is encourage someone to engage in help-seeking behaviours, and cannot force them into treatment unless they are at risk of harm to themselves and/or others. Which is when you get the CAT Team involved for an assessment.
Sometimes this is helpful when someone is experiencing psychosis symptoms like Schizophrenia, but can be very distressing. So it is best they initially seek help from their GP.
There are lots of carer on thsi forum with experiences of this, you might like to Introduce Yourself Here as that can be a good way of connecting with other members, I look forward to getting to know you better,
Lunar