A controlled trial was done on postmenopausal women with rheumatoid arthritis (NLM) and the results were positive. The subjects received 50mg every 3 weeks (if memory serves correctly) and there was a significant increase in Hgb. Deca is one of may AAS that are notable for increasing Hgb and Hct.
However, even though your mother would not be "cycling" it would be imperative to have bloods drawn regularly just the same. No two bodies produces RBC's at the exact same rate and the introduction of AAS into the system could cause a rapid increase in RBC's over a short period of time. Is it guaranteed to be quick? No? But it is possible...At least in my own personal experience.
As a healthcare professional, I am amazed at how under utilized anabolics are! The benefits often outweigh the risks, but is never an option to people.