Low libido can be caused by different things. 1/ hormonal changes (a hormonal blood panel test would show if there is any abnormalities 2/ depression, 3/ some medications, 4/ you've mentioned possible emotional/psychological factors. If she is in her 50's it may be very possible that the former are the causes.
There are some options to address this. 1/ taking supplements with androgen properties (if she is not interested in hormonal treatment) These can be - Maca, Macuna Pruriens, Tribulus, DHEA or Prgnenolone. These can be purchased at a health store or online.
Another option if her behavior is more of a psychological/emotional nature would be to consider counseling, use self help materials ie bibliotherapy, autosuggestion CD, hypnotherapy (if you as Christian are open to this modality)