Herrena - good luck for your mum and you tomorrow.
I do remember when I was first DX, I was too scared to want too much information, I found everything they said frightening and only heard the negatives words, which terrified me. I suppose I am saying your mum might feel a bit like this, in time I came to want to know as much as I could about my illness, but it took a while.
In my case, my DH stayed and asked the consultant questions, while I went and had a cup of tea with my breast care nurse 
, DH needed information, just as you feel you do, but I only wanted to know the minimum necessary.
Your mum has the right to be told whatever information she asks for, - but she also has the right not to hear it if she's not ready. So if there are things you want to know about, just check with her, so she's got the chance to leave the room if she doesn't want to hear.
In all probability she'll ask you to relay the info. at a slightly later date.
The trouble is, appointments come along very quickly, and in your head you are still trying to deal with the fact you have cancer, - there's a lot of denial, - and talking about it can be very, very hard. You feel a bit like a 'case' being discussed, and sometimes its as if people aren't even talking about you - you think it must be someone else - this can't be happening to you. It is weird.
Of course - I might have got hold of the wrong end of the stick entirely as regards your mum - so feel free to completely ignore me, or file me under 'L' for 'loon'
But I just thought I'd say, in case it was helpful 
loads of good vibes for tomorrow. x