I am so sorry to hear about your sons shabba. I think the mind would do all sorts of things to process and cope with that.
ZZZ one final question - do the voices always talk to DD, or do they ever talk to each other?
And do they ever talk about her, rather than directly to her? I.e. do they say "we like DD" or "DD is a friend".
Do they describe what she is doing "she is washing up now", "she is having a shower"?
Do they describe her feelings, either before or after she feels them?
Do they tell her to do anything other than "come here"?
Does she ever hear music or noises rather than voices?
I dont mean to seem like I'm interrogating you, but those are some of the different categories of hallucination. If you can work out what kind it is it's much easier to think about whether it's a problem or not.
Oh, and does she ever experience anything else that isn't there? Not just sights, but smells, tastes or sensations? (they happen in all 5 senses).
(caveat: I am only a medical student, so I'm not at all qualified to make any kind of diagnosis, but I just thought I'd run through some of the possibilities that I know of for you)
As you said though, she's hearing very little, so I really think it's nothing to worry about.
Carrots no more of a fruitcake than any of the rest of us if we'd admit it! :)