If you are active duty and if you are the source of support for your mother you can make an attempt to get her certified as a dependent.
Check out the documentation....
http://www.dtic.mil/whs/directives/infomgt/forms/eforms/dd0137-3.pdf
INSTRUCTIONS
The member must complete Items 1 and 2, and sign and date the form. Parent or parent(s) representative (if parent is unable to
complete the form due to health or physical disability) must complete Items 3 through 12, sign and date the form, and have the form
notarized. If a representative completes the form for the parent(s), include in the Remarks section the name of the individual, the
relationship, and the reason the form was not completed by parent(s). If the member is deceased, information furnished must reflect
the 12 months prior to member's death.
NOTES: Answer all questions. If any question does not apply, write "NOT APPLICABLE" or "N/A" in that block. Use the Remarks section when
required. Incomplete answers will delay final action on the application. Verification of all income is required. Proof of member's contribution is
required when applying for Basic Allowance for Housing (BAH). Parent must be more than 50% dependent upon member.