still calling me saying she can’t cope anymore
To cut a long story short, she has now said that she has met someone on a suicide forum and plans to meet up with them at the weekend and ‘do it’ what do I do? What can I do?
This sounds like emotional blackmail.
I have helped her get help
And on medication … I don’t know what to do?
I would urge that you don't deal with this alone, and please let professionals handle it. You are in the UK, and I'm not sure what your emergency service numbers are. It's 911 in NA.
If they are threatening suicide and you are concerned that they are in danger, dial your local emergency services. Don't handle this on your own.