Herrena - I think it's good they are starting her on her chemo soon - no reason not to get it underway, and she will feel she is moving forwards.
I'm sorry I can't remember if she has had surgery, or is having chemo first (different hospitals seem to take different approaches - both equally successful as far as I can tell) - if the latter, have they said when they are likely to do her surgery?
I think wanting someone to say 'it will all be fine' is very normal, - we've all wanted that! - but BC is the one where they never say that (and I sure some other cancers too) - the treatment is a long haul, and you sort of have to get used to there being no quick answers or reassurances.
But I certainly don't think you are offering her false hope, - IIRC they think her lymph nodes are clear, - which is excellent, but even if it has reached the nodes - that's really what lymph nodes are there for - to catch the rubbish before and stop it getting into your system.
But at the start it is very very hard not to be negative, it is such a shock, and so frightening, it will be constantly in her mind, and everything that the professionals say to her, she will be thinking over and interpreting and worrying about.
So if you can offer her lots of reassurance, she may gradually start to relax a little bit. And honestly once treatment starts, you do begin to feel a bit better (mentally I mean - obviously physically you feel a bit pants!) you feel as if something is being done, and you get into a sort of hospital and treatment routine, and there is reassurance in seeing medical people regularly.
And I used to find my BCN was very good at calming me down when medical people said somewhat tactless things, and explaining things.
If your mum does find she's struggling with the emotional side of things (and I found that much harder to cope with than the physical stuff) she should talk to her BCN or her onc team. there is help available - counselling, relaxation, or even medication if she feels she needs help.
Apologies for another long essay - there is so much in what you say about you mum that reminds me of how I felt. Cancer is an utterly shit thing to happen to anyone, and I felt so bewildered and scared at the beginning, so I have enormous sympathy for your mum, - I wish her all the very best in her treatment, and hope she starts to feel a little less lost and anxious once her treatment gets going 