B12 injections may be purchased over the counter in Canada. The following website carries it under the name "Cyanocobalamin injection":
http://www.canadadrugsuperstore.com/more.asp?ProductID=25273
I would only consider this under the direct knowledge of her Primary Doctor though.
Many studies are reporting success with sublingual B12 instead. It is absorbed into the blood stream, but without the injection.
I did find evidence supporting 5mg B12 injections for severe fatigue and Fibromyalgia.
Perhaps printing supporting articles for her Doctor will help:
http://www.mayoclinic.com/health/vitamin-B12/NS_patient-vitaminb12
http://www.wholehealthmd.com/print/view/1,1560,AR_1045,00.html
http://www.immunesupport.com/library/showarticle.cfm/id/1287
I would not resort to Veterinary Medicine.
I care for a mother who is ill as well and I appreciate your "stop at nothing" approach when you find something that works.
I truly hope this helps-if it does please accept.
If you need more info or clarification please contact me.
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I hope my information is helpful. If you have more questions, just ask! I will gladly help, otherwise please click "accept".
Positive feedback and any bonus would be appreciated. Thank you, Christy