Have they tested your Mom's serum B12, folate, iron, MMA and homocystine levels? If her levels are within the normal range, I doubt that they would prescribe B12 injections. However, in our experience, if B12 is less than 500, she probably could benefit from B12. The oral methlycolbamin form of B12 is just as effective as a B12 injection and you can get this over the counter. We use the Jarrow brand and order it from
www.iherb.com. Many doctors do not know this and they also continue use reference ranges that are no longer supported by the broader international medical community. Meaning that they feel anything under 500 is OK even in the presence of symptoms....hematological and neurological symptoms. A standard b12 level does not reflect tissue levels of B12 that's why they should check her MMA and Homocycstine.
If you supplement with B12, be sure to take a B complex also. You need all the B vitamins especially folate. Supplementing with just one can mask other problems.