B2 visa and Being a Public Charge

B2 visa can be sponsored by a US citizen. http://www.uscis.gov/sites/default/files/files/form/i-134.pdf

Relying on US welfare will affect her future B2 visa application

http://www.nolo.com/legal-encyclopedia/b-2-visa-us-medical-treatment-who-qualifies.html

You Must Show That You Can Pay for Your Treatment
The price of U.S. medical services can come as a shock to visitors who are accustomed to government-subsidized care in their home countries. You will need to show U.S. government officials that you have adequate financial resources to pay for the medical treatment that you need. You will not be able to rely on any U.S. welfare or public assistance, because the law says that people who are likely to become a “public charge” will not be eligible for a B-2 visa.