If she is only coming for a visit, I'd refrain from using the term 'sponsorship'.

Please understand that the only way to receive a visitor's visa is to make sure the consular believes she is going to return. Besides that the way she communicates also plays a pivotal role.

I sent following documents for my parents and have been doing that for quite sometime whenever their visa expired (you might find this overwhelming, but I suggest you consolidate all documents than leave out few and take chances)-

From my end
1. Copy of my passport (or a green card)
2. Copy of my driver's license
3. Copy of my work's access badge or a letter of employment (this might be redundant, but still....)
4. Some pay stubs of recent months
5. Copy of my social security card (again, this is redundant but I'd send it anyway)
6. Copy of my mortgage (same as above)
7. Bank statement
8. A VERY GOOD letter to the embassy explaining why you want to invite them, how long they are going to be here, what will you guys do, where will you visit, and write something that your parents will not overstay or work illegally or become a liability of this nation. 

From their end
1. Any employment documentation (past or present).
2. Bank statement
3. Property papers
4. Citizenship papers
5. Proof that I am their son
6. Copies of previous travel visas ( I don't know why I'd ask them to insert these but I believe it will perhaps make the consular believe they have travelled before and returned)
7. A VERY GOOD letter to the embassy confirming they will return before the visa expires and will not do anything to put their visa status in jeopardy.

Once again, this is what I do every five years, and it has worked 100% of the time, I am sure someoene else will suggest you something else, but if you have these documents handy, and them as well, as your mom to apply for visa after you fedex them your documents.