So sorry about your mom but glad it was caught early. You are right, there is so much information and it is so overwhelming making treatment choices.
The web, in general is good to get basic breast cancer information. A book that is helpful is Dr. Susan Love's breast book. - It is a little detailed and technical but is a good basic resource. Finding a good breast surgeon and oncologist is half the battle. They should take alot of time with your mom, explaining all the treatment/surgery options for her particular situation. Be sure to get a copy of her pathology report and have them explain that to her. It is very scary at first, but things will get a little better, once a treatment plan is in place.
I have a family hx too and have been collecting articles re breast cancer for years, "just in case." Thought I had escaped the family curse, as I had almost made it to 50, but low and behold I was dxed at 48 in 06. Mine was found early too, on mammogram and doing well so far.
Might add ,my mom is a 28yr survivor, dxed with a large 6.2cm tumor. Only had L mastectomy, no other treatment, but yet here she is almost 30yrs later. Your mom will make it too.
Best wishes to you and your family.