How do I tell my 6yo that someone close to us has terminal cancer?

It's all in the title really. A close family friend was diagnosed with terminal cancer at the start of the year. Doctors say months and to get her affairs in order. I think it's important that my daughter knows what's happening so she's not blindsided when she actually dies but I'm struggling with how to tell her in an age appropriate way.

Any and all advice is massively appreciated, I have already spoken to a psychologist friend who has give some great tips and resources but honestly I'm still questioning myself and how to do it "right" or "properly" or simply wo causing too much pain or trauma.