Support includes food, clothing, shelter, entertainment, gifts, schooling, healthcare, medical expenses, and anything else purchased or used for the benefit of the person.
If there is a question about support, have your mother see that your sister saves enough money in the bank that it will push your mother over 50% of support. Money put in savings is not considered used for support.
Your sister's income also needs to be less than $3100 for the year, NOT including social security.
This post does not create an agreement to represent you before the IRS, nor does it invoke confidentiality regulations. Postings are based only on the information provided and you should consult a tax professional in your area before relying on information contained in this post.