Hi mamteur - I had grade 3 BC five years ago, mine had spread to my lymph nodes. I had mastectomy, lymph node clearance, radiotherapy, herceptin and am currently on tamoxifen.
what treatment your mum has will depend on the stage of her cancer and whether it has spread to nodes (it's good that they think not - that means she will probably avoid chemo and that her 'stage' number will be lower) and also on what type of cancer she has (i.e. if it is a hormonal type, and receptive to herceptin or tamoxifen treatment)
It is a shocking DX and your mum is probably feeling scared but as you say not wanting to scare or worry you. The early days when you are waiting to find out exactly what is going on are the most anxious IME. Once your mum has a treatment plan she (and you) will feel as if it's being dealt with.
My advice for what its worth is for her to have someone go to apointments with her if possible (it's hard to take everything in on your own) and to write down anything she wants to ask as she thinks of it, and take a list in with her - so she gets the most out of her consultant appointments and gets all her questions addressed.
If you've got any question you think I might be able to help with - please do ask, I'm happy to answer as best I can on any aspect of treatment, surgery etc.
Also - I am a regular on the Tamoxifen thread here on general health - lots of ladies there with lots of experience - they'd be more than happy to answer any questions you or your mum may have - just dive in with any queries, you'll be made very welcome 